CINXE.COM

<!doctype html> <html lang="en-US"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="profile" href="https://gmpg.org/xfn/11"> <script id="Cookiebot" src="https://consent.cookiebot.com/uc.js" data-cbid="095b91a6-f087-4380-b01d-e44b1c2af358" data-blockingmode="auto" type="text/javascript"></script>  <script async src="https://www.googletagmanager.com/gtag/js?id=G-XYTVD2CXR4"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-XYTVD2CXR4'); </script> <title>Recent Advances on Principles of Concurrent Data Structures – Communications of the ACM</title> <meta name='robots' content='max-image-preview:large' /> <style>img:is([sizes="auto" i], [sizes^="auto," i]) { contain-intrinsic-size: 3000px 1500px }</style> <link rel='dns-prefetch' href='//stats.wp.com' /> <link rel="alternate" type="application/rss+xml" title="Communications of the ACM » Feed" href="https://cacm.acm.org/feed/" /> <link rel="alternate" type="application/rss+xml" title="Communications of the ACM » Comments Feed" href="https://cacm.acm.org/comments/feed/" /> <link rel="alternate" type="application/rss+xml" title="Communications of the ACM » Recent Advances on Principles of Concurrent Data Structures Comments Feed" href="https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/feed/" /> <script class="wp-asset-manager usage-logger" type="text/javascript">window.amScripts = window.amScripts || {}; window.amScripts["usage-logger"] = {"nonce":"06b4bc800f","id":758290,"type":"digital-library","doi":"10.1145\/3653290"}</script><style class="wp-asset-manager cacm-global-critical" type="text/css">@font-face{font-display:swap;font-family:Inter;font-style:normal;src:url(../be7cb18dc7caf47cf7e9.woff2) format("woff2"),url(../817c4274293e221c5076.woff) format("woff")}@font-face{font-display:swap;font-family:Inter;font-style:normal;font-weight:700;src:url(../54321e26b8bf4739a16d.woff2) format("woff2"),url(../7ad0df5561cc0933cead.woff) format("woff")}@font-face{font-display:swap;font-family:Work Sans;font-style:normal;font-weight:500;src:url(../2dd7c3c79fd1aa1d85ca.woff2) format("woff2"),url(../9a8cbe3b3bec955df411.woff) format("woff")}@font-face{font-display:swap;font-family:Work Sans;font-style:normal;font-weight:700;src:url(../ab8702255905c24de1c1.woff2) format("woff2"),url(../9ab52d2504cfe145b9bd.woff) format("woff")}@font-face{font-display:swap;font-family:Work Sans;font-style:normal;font-weight:800;src:url(../cef488e4e9f273a0a1e3.woff2) format("woff2"),url(../a99bf2b51c426338ae2c.woff) format("woff")}html{box-sizing:border-box}html *,html :after,html :before{box-sizing:inherit}a,abbr,address,article,aside,audio,b,blockquote,body,canvas,caption,cite,code,dd,del,details,dfn,div,dl,dt,em,embed,fieldset,figcaption,figure,footer,form,h1,h2,h3,h4,h5,h6,header,html,i,iframe,img,ins,kbd,label,legend,li,mark,menu,nav,object,ol,output,p,pre,q,ruby,s,samp,section,small,span,strike,strong,sub,summary,sup,table,tbody,td,tfoot,th,thead,time,tr,u,ul,var,video{margin:0;padding:0;border:0;font-size:100%;font:inherit;vertical-align:baseline}article,aside,details,figcaption,figure,footer,header,menu,nav,section{display:block}ol,ul{list-style:none}blockquote,q{quotes:none}blockquote:after,blockquote:before,q:after,q:before{content:"";content:none}table{border-collapse:collapse;border-spacing:0}fieldset{border:none;margin:0;padding:0}button,input,select,textarea{-webkit-appearance:none;-moz-appearance:none;appearance:none;border:0;border-radius:0;font:inherit;margin:0}button{background-color:transparent;padding:0}body,html{font-family:var(--wp--preset--font-family--inter);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}html{scroll-padding-top:var(--wp--custom--siteheader-height)!important}body{overflow-x:hidden}a img{display:block}img{height:auto;max-width:100%}svg{display:block}.container{margin-left:auto;margin-right:auto;width:calc(min(100%,var(--wp--style--global--wide-size) + var(--wp--custom--site-edge)*2) - var(--wp--custom--site-edge)*2)}.screen-reader-only{border:0;clip:rect(0,0,0,0);height:1px;margin:-1px;padding:0;width:1px}.screen-reader-only,.skip-link{overflow:hidden;position:absolute}.skip-link{margin-left:auto;margin-right:auto;background-color:var(--wp--preset--color--white);color:inherit;left:0;opacity:0;padding:.625rem;right:0;text-align:center;text-decoration:none;top:0;transform:translateY(-100%);width:-moz-max-content;width:max-content;z-index:-1}.skip-link:focus{opacity:1;transform:translateY(0);z-index:2147483647}.site-content{padding-top:var(--wp--custom--siteheader-height)}@media(min-width:48rem){.site-content{padding-top:var(--wp--custom--siteheader-height)}}.site-header-hamburger-menu[aria-hidden=true]{display:none}.site-header-membership-nav{align-self:stretch;display:flex;position:relative}.site-header--expanded .site-header-membership-nav,.site-header:not(.site-header--member-logged-in) .site-header-membership-nav{display:none}.site-header{position:fixed;width:100%;z-index:7}.site-header--expanded{height:100%}.site-header--no-js{opacity:0}.site-header.headroom{transition:transform .2s linear;will-change:transform}.site-header.headroom--pinned{transform:translateY(0)}.site-header.headroom--unpinned{height:auto;transform:translateY(-100%)}.site-header-container{align-items:center;background-color:var(--wp--preset--color--white);border-bottom:var(--wp--custom--border-gray);display:flex;gap:1rem;height:var(--wp--custom--siteheader-height);justify-content:space-between;padding:0 1rem}.site-header-container a{text-decoration:none}.site-header-container a:active,.site-header-container a:focus,.site-header-container a:hover{text-decoration:underline;text-decoration-color:inherit;text-decoration-thickness:1px;text-underline-offset:2.5px}@media(min-width:37.5rem){.site-header-container{padding:0 1.5rem}}@media(min-width:48rem){.site-header-container{padding:0 0 0 1rem}}@media(min-width:64rem){.site-header-container{gap:2.25rem}}@media(min-width:80rem){.site-header-container{gap:3rem}}.site-header--member-logged-in .site-header-container{padding:0 0 0 1rem}@media(min-width:37.5rem){.site-header--member-logged-in .site-header-container{padding:0 0 0 1.5rem}}.site-header--expanded .site-header-container{background-color:var(--wp--preset--color--cacm-darker-blue)}@media(max-width:47.9375rem){.site-header-logo,.site-header-search{margin-left:auto}}.site-header-member-login-link{font-weight:var(--wp--custom--font-weight-bold)}.site-header-member-login-link[aria-hidden=true]{visibility:hidden}@media(max-width:47.9375rem){.site-header-member-login-link{display:none}}.site-header--member-logged-in .site-header-member-login-link{display:none}.site-header-magazine-menu,.site-header-topics-menu{position:relative}.site-header-magazine-menu-toggle,.site-header-topics-menu-toggle{font-size:.9375rem;font-weight:var(--wp--custom--font-weight-regular);line-height:1.21;align-items:center;cursor:pointer;display:flex;gap:.3333333333rem}@media(min-width:80rem){.site-header-magazine-menu-toggle,.site-header-topics-menu-toggle{font-size:1rem;font-weight:var(--wp--custom--font-weight-regular);line-height:1.21;gap:.65625rem}}.site-header-magazine-menu-toggle[aria-hidden=true],.site-header-topics-menu-toggle[aria-hidden=true]{visibility:hidden}.site-header-magazine-menu-toggle[aria-expanded=true]>svg,.site-header-topics-menu-toggle[aria-expanded=true]>svg{transform:rotate(180deg)}.site-header-magazine-menu-toggle:focus,.site-header-magazine-menu-toggle:hover,.site-header-topics-menu-toggle:focus,.site-header-topics-menu-toggle:hover{text-decoration:underline}.site-header-magazine-menu-expanded,.site-header-topics-menu-expanded{background-color:var(--wp--preset--color--white);border-radius:.3125rem;box-shadow:0 .125rem .25rem -.125rem rgba(24,39,75,.12),0 .25rem .25rem -.125rem rgba(24,39,75,.08);display:flex;gap:1.875rem;justify-content:space-between;padding:1.75rem 1.875rem 1.5rem;position:absolute;right:0;text-align:left;top:2.28125rem;white-space:nowrap;z-index:4}.site-header-magazine-menu-expanded[aria-hidden=true],.site-header-topics-menu-expanded[aria-hidden=true]{display:none}@media(max-width:47.9375rem){.site-header-magazine-menu,.site-header-topics-menu{display:none}}.site-header:not(.site-header--member-logged-in) .site-header-topics-menu-expanded{left:0;right:auto}</style><style class="wp-asset-manager cacm-article-critical" type="text/css">.article-header{left:50%;margin-left:-50vw;margin-right:-50vw;position:relative;right:50%;width:100vw;background-color:var(--cacm--article-header--background-color);border-bottom:1px solid var(--cacm--article-header--border-color);color:var(--cacm--article-header--text-color);margin-bottom:var(--wp--custom--gap)}@media(min-width:48rem){.article-header{grid-area:header;margin-bottom:1.5rem}}.article-header__inner{--wp--custom--vertical-block-rhythm:0.5rem;padding:2rem 0 0}@media(min-width:48rem){.article-header__inner{--wp--custom--vertical-block-rhythm:0.625rem;display:grid;gap:0 var(--cacm--article--gap);grid-template-columns:auto 1fr;padding:var(--cacm--article--gap) 0}}@media(min-width:64rem){.article-header__inner{grid-template-columns:var(--cacm--article--sidebarleft--width) 1fr}}.article-header__section{margin-bottom:var(--wp--custom--vertical-block-rhythm);display:inline-block}.article-header__section:last-child{margin-bottom:0}.article-header__section a{text-decoration:none}.article-header__section a:active,.article-header__section a:focus,.article-header__section a:hover{text-decoration:underline;text-decoration-color:inherit;text-decoration-thickness:1px;text-underline-offset:2.5px}@media(max-width:47.9375rem){.article-header__section{margin-right:.625rem}}@media(min-width:48rem){.article-header__section{grid-column:1/1;text-align:right}}.article-header__section>a{font-size:.875rem;font-weight:700;line-height:1.2142857143;background-color:var(--cacm--article-header--button--background-color);color:var(--cacm--article-header--button--text-color);display:inline-block;padding:.3125rem .625rem;text-transform:uppercase}@media(min-width:48rem){.article-header__figure,.article-header__meta,.article-header__share,.article-header__subtitle,.article-header__title,.article-header__topic-and-issue-section{grid-column:2/2}}.article-header__topic-and-issue-section{--wp--custom--vertical-block-rhythm:0.5rem;margin-bottom:var(--wp--custom--vertical-block-rhythm);font-size:.9375rem;line-height:1.5333333333;font-family:var(--wp--preset--font-family--inter);display:flex;flex-direction:column}.article-header__topic-and-issue-section:last-child{margin-bottom:0}@media(min-width:48rem){.article-header__topic-and-issue-section{--wp--custom--vertical-block-rhythm:1.25rem;align-items:center;flex-direction:row;gap:2rem}}.article-header__issue-section{color:var(--cacm--article-header--text-color)}.article-header__title{margin-bottom:var(--wp--custom--vertical-block-rhythm);font-family:var(--wp--preset--font-family--work-sans);font-size:var(--wp--preset--font-size--work-md);line-height:32.2px;font-weight:var(--wp--custom--font-weight-extrabold)}.article-header__title:last-child{margin-bottom:0}@media(min-width:48rem){.article-header__title{font-size:var(--wp--preset--font-size--work-xxxl);line-height:50.4px;font-weight:var(--wp--custom--font-weight-extrabold)}}@media(min-width:64rem){.article-header__title{font-size:var(--wp--preset--font-size--work-xxl);line-height:44.28px;font-weight:var(--wp--custom--font-weight-extrabold)}}.article-header__subtitle{font-family:var(--wp--preset--font-family--work-sans);font-size:var(--wp--preset--font-size--work-xxs);line-height:22.5px;font-weight:var(--wp--custom--font-weight-bold);font-size:1.3125rem;line-height:1.2380952381;letter-spacing:-.08px;font-weight:var(--wp--custom--font-weight-medium);letter-spacing:-.03125rem;margin-bottom:.125rem}.article-header__subtitle:last-child{margin-bottom:0}.article-header__subtitle a{word-break:break-word}.article-header__subtitle b,.article-header__subtitle strong{font-weight:var(--wp--custom--font-weight-bold)}.article-header__subtitle em,.article-header__subtitle i{font-style:italic}.article-header__subtitle del,.article-header__subtitle strike{text-decoration:line-through}.article-header__subtitle sub,.article-header__subtitle sup{font-size:75%;line-height:0;position:relative}.article-header__subtitle sub{bottom:-.25em}.article-header__subtitle sup{top:-.5em}.article-header__subtitle .monospace,.article-header__subtitle p code{font:var(--wp--custom--font-weight-regular) 90%/1.6 Courier,monospace}@media(min-width:48rem){.article-header__subtitle{--wp--custom--vertical-block-rhythm:1.25rem;font-family:var(--wp--preset--font-family--work-sans);font-size:var(--wp--preset--font-size--work-xs);line-height:25.2px;font-weight:var(--wp--custom--font-weight-bold);font-size:1.5625rem;line-height:1.2;letter-spacing:-.1px;font-weight:var(--wp--custom--font-weight-medium);letter-spacing:-.03125rem;margin:.5rem 0 .625rem}.article-header__subtitle:last-child{margin-bottom:0}}.article-header__meta{margin-bottom:var(--wp--custom--vertical-block-rhythm);font-size:.9375rem;line-height:1.5333333333;font-family:var(--wp--preset--font-family--inter);display:flex;flex-direction:column}.article-header__meta:last-child{margin-bottom:0}.article-header__meta>*{margin-bottom:var(--wp--custom--vertical-block-rhythm)}.article-header__meta>:last-child{margin-bottom:0}.article-header__byline{margin-top:.625rem}.article-header__byline>a{border-bottom:1px dotted var(--cacm--article-header--byline--text-color);color:var(--cacm--article-header--byline--text-color);text-decoration:none}@media(max-width:47.9375rem){.article-header__figure{left:50%;margin-left:-50vw;margin-right:-50vw;position:relative;right:50%;width:100vw}}@media(min-width:48rem){.article-header__figure{display:flex;flex-direction:column}}.article-header__figure .image-wrapper{margin-bottom:var(--wp--custom--vertical-block-rhythm)}.article-header__figure .image-wrapper:last-child{margin-bottom:0}@media(min-width:64rem){.article-header__figure .image-wrapper{grid-column:1/1}}.article-header__figure .image-wrapper>img{-o-object-fit:cover;object-fit:cover}.article-header__figure .video-wrapper{height:100%;overflow:hidden;position:relative;width:100%;padding-bottom:56.25%}.article-header__figure .video-wrapper>iframe{height:100%;left:0;-o-object-fit:contain;object-fit:contain;position:absolute;top:0;width:100%}.article-header__figure .video-wrapper>:not(iframe){display:none}.article-header__figure figcaption{font-size:.9375rem;line-height:1.4666666667;font-family:var(--wp--preset--font-family--inter);color:var(--cacm--article-header--caption--text-color)}@media(max-width:47.9375rem){.article-header__figure figcaption{margin:0 var(--wp--custom--site-edge)}}@media(min-width:64rem){.article-header__figure figcaption{grid-column:2/2;margin:0}}.article-header__figure figcaption>p.article-header--credit{font-style:italic}</style><link rel="preload" href="https://cacm.acm.org/wp-content/themes/cacm/client/src/fonts/inter-v12-latin-regular.woff2" class="wp-asset-manager cacm-font-inter-regular-woff2" as="font" media="all" type="font/woff2" crossorigin /><link rel="preload" href="https://cacm.acm.org/wp-content/themes/cacm/client/src/fonts/inter-v12-latin-700.woff2" class="wp-asset-manager cacm-font-inter-700-woff2" as="font" media="all" type="font/woff2" crossorigin /><link rel="preload" href="https://cacm.acm.org/wp-content/themes/cacm/client/src/fonts/work-sans-bold.woff2?ver=1.0.0" class="wp-asset-manager cacm-font-work-sans-700-woff2" as="style" media="all" type="font/woff2" /><link rel="preload" href="https://cacm.acm.org/wp-content/themes/cacm/client/src/fonts/work-sans-extrabold.woff2?ver=1.0.0" class="wp-asset-manager cacm-font-work-sans-800-woff2" as="style" media="all" type="font/woff2" /><script type="text/javascript"> /* <![CDATA[ */ window._wpemojiSettings = {"baseUrl":"https:\/\/s.w.org\/images\/core\/emoji\/15.0.3\/72x72\/","ext":".png","svgUrl":"https:\/\/s.w.org\/images\/core\/emoji\/15.0.3\/svg\/","svgExt":".svg","source":{"concatemoji":"https:\/\/cacm.acm.org\/wp-includes\/js\/wp-emoji-release.min.js?ver=6.7.1"}}; /*! This file is auto-generated */ !function(i,n){var o,s,e;function c(e){try{var t={supportTests:e,timestamp:(new Date).valueOf()};sessionStorage.setItem(o,JSON.stringify(t))}catch(e){}}function p(e,t,n){e.clearRect(0,0,e.canvas.width,e.canvas.height),e.fillText(t,0,0);var t=new Uint32Array(e.getImageData(0,0,e.canvas.width,e.canvas.height).data),r=(e.clearRect(0,0,e.canvas.width,e.canvas.height),e.fillText(n,0,0),new Uint32Array(e.getImageData(0,0,e.canvas.width,e.canvas.height).data));return t.every(function(e,t){return e===r[t]})}function u(e,t,n){switch(t){case"flag":return n(e,"\ud83c\udff3\ufe0f\u200d\u26a7\ufe0f","\ud83c\udff3\ufe0f\u200b\u26a7\ufe0f")?!1:!n(e,"\ud83c\uddfa\ud83c\uddf3","\ud83c\uddfa\u200b\ud83c\uddf3")&&!n(e,"\ud83c\udff4\udb40\udc67\udb40\udc62\udb40\udc65\udb40\udc6e\udb40\udc67\udb40\udc7f","\ud83c\udff4\u200b\udb40\udc67\u200b\udb40\udc62\u200b\udb40\udc65\u200b\udb40\udc6e\u200b\udb40\udc67\u200b\udb40\udc7f");case"emoji":return!n(e,"\ud83d\udc26\u200d\u2b1b","\ud83d\udc26\u200b\u2b1b")}return!1}function f(e,t,n){var r="undefined"!=typeof WorkerGlobalScope&&self instanceof WorkerGlobalScope?new OffscreenCanvas(300,150):i.createElement("canvas"),a=r.getContext("2d",{willReadFrequently:!0}),o=(a.textBaseline="top",a.font="600 32px Arial",{});return e.forEach(function(e){o[e]=t(a,e,n)}),o}function t(e){var t=i.createElement("script");t.src=e,t.defer=!0,i.head.appendChild(t)}"undefined"!=typeof Promise&&(o="wpEmojiSettingsSupports",s=["flag","emoji"],n.supports={everything:!0,everythingExceptFlag:!0},e=new Promise(function(e){i.addEventListener("DOMContentLoaded",e,{once:!0})}),new Promise(function(t){var n=function(){try{var e=JSON.parse(sessionStorage.getItem(o));if("object"==typeof e&&"number"==typeof e.timestamp&&(new Date).valueOf()<e.timestamp+604800&&"object"==typeof e.supportTests)return e.supportTests}catch(e){}return null}();if(!n){if("undefined"!=typeof Worker&&"undefined"!=typeof OffscreenCanvas&&"undefined"!=typeof URL&&URL.createObjectURL&&"undefined"!=typeof Blob)try{var e="postMessage("+f.toString()+"("+[JSON.stringify(s),u.toString(),p.toString()].join(",")+"));",r=new Blob([e],{type:"text/javascript"}),a=new Worker(URL.createObjectURL(r),{name:"wpTestEmojiSupports"});return void(a.onmessage=function(e){c(n=e.data),a.terminate(),t(n)})}catch(e){}c(n=f(s,u,p))}t(n)}).then(function(e){for(var t in e)n.supports[t]=e[t],n.supports.everything=n.supports.everything&&n.supports[t],"flag"!==t&&(n.supports.everythingExceptFlag=n.supports.everythingExceptFlag&&n.supports[t]);n.supports.everythingExceptFlag=n.supports.everythingExceptFlag&&!n.supports.flag,n.DOMReady=!1,n.readyCallback=function(){n.DOMReady=!0}}).then(function(){return e}).then(function(){var e;n.supports.everything||(n.readyCallback(),(e=n.source||{}).concatemoji?t(e.concatemoji):e.wpemoji&&e.twemoji&&(t(e.twemoji),t(e.wpemoji)))}))}((window,document),window._wpemojiSettings); /* ]]> */ </script> <style id='wp-emoji-styles-inline-css' type='text/css'> img.wp-smiley, img.emoji { display: inline !important; border: none !important; box-shadow: none !important; height: 1em !important; width: 1em !important; margin: 0 0.07em !important; vertical-align: -0.1em !important; background: none !important; padding: 0 !important; } </style> <link rel='stylesheet' id='wp-block-library-css' href='https://cacm.acm.org/wp-includes/css/dist/block-library/style.min.css?ver=6.7.1' type='text/css' media='all' /> <link rel='stylesheet' id='mediaelement-css' href='https://cacm.acm.org/wp-includes/js/mediaelement/mediaelementplayer-legacy.min.css?ver=4.2.17' type='text/css' media='all' /> <link rel='stylesheet' id='wp-mediaelement-css' href='https://cacm.acm.org/wp-includes/js/mediaelement/wp-mediaelement.min.css?ver=6.7.1' type='text/css' media='all' /> <style id='jetpack-sharing-buttons-style-inline-css' type='text/css'> .jetpack-sharing-buttons__services-list{display:flex;flex-direction:row;flex-wrap:wrap;gap:0;list-style-type:none;margin:5px;padding:0}.jetpack-sharing-buttons__services-list.has-small-icon-size{font-size:12px}.jetpack-sharing-buttons__services-list.has-normal-icon-size{font-size:16px}.jetpack-sharing-buttons__services-list.has-large-icon-size{font-size:24px}.jetpack-sharing-buttons__services-list.has-huge-icon-size{font-size:36px}@media print{.jetpack-sharing-buttons__services-list{display:none!important}}.editor-styles-wrapper .wp-block-jetpack-sharing-buttons{gap:0;padding-inline-start:0}ul.jetpack-sharing-buttons__services-list.has-background{padding:1.25em 2.375em} </style> <style id='elasticpress-facet-style-inline-css' type='text/css'> .widget_ep-facet input[type=search],.wp-block-elasticpress-facet input[type=search]{margin-bottom:1rem}.widget_ep-facet .searchable .inner,.wp-block-elasticpress-facet .searchable .inner{max-height:20em;overflow:scroll}.widget_ep-facet .term.hide,.wp-block-elasticpress-facet .term.hide{display:none}.widget_ep-facet .empty-term,.wp-block-elasticpress-facet .empty-term{opacity:.5;position:relative}.widget_ep-facet .empty-term:after,.wp-block-elasticpress-facet .empty-term:after{bottom:0;content:" ";display:block;left:0;position:absolute;right:0;top:0;width:100%;z-index:2}.widget_ep-facet .level-1,.wp-block-elasticpress-facet .level-1{padding-left:20px}.widget_ep-facet .level-2,.wp-block-elasticpress-facet .level-2{padding-left:40px}.widget_ep-facet .level-3,.wp-block-elasticpress-facet .level-3{padding-left:60px}.widget_ep-facet .level-4,.wp-block-elasticpress-facet .level-4{padding-left:5pc}.widget_ep-facet .level-5,.wp-block-elasticpress-facet .level-5{padding-left:75pt}.widget_ep-facet input[disabled],.wp-block-elasticpress-facet input[disabled]{cursor:pointer;opacity:1}.widget_ep-facet .term a,.wp-block-elasticpress-facet .term a{-webkit-box-align:center;-ms-flex-align:center;align-items:center;display:-webkit-box;display:-ms-flexbox;display:flex;position:relative}.widget_ep-facet .term a:hover .ep-checkbox,.wp-block-elasticpress-facet .term a:hover .ep-checkbox{background-color:#ccc}.ep-checkbox{-webkit-box-align:center;-ms-flex-align:center;-ms-flex-negative:0;-webkit-box-pack:center;-ms-flex-pack:center;align-items:center;background-color:#eee;display:-webkit-box;display:-ms-flexbox;display:flex;flex-shrink:0;height:1em;justify-content:center;margin-right:.25em;width:1em}.ep-checkbox:after{border:solid #fff;border-width:0 .125em .125em 0;content:"";display:none;height:.5em;-webkit-transform:rotate(45deg);transform:rotate(45deg);width:.25em}.ep-checkbox.checked{background-color:#5e5e5e}.ep-checkbox.checked:after{display:block} </style> <link rel='stylesheet' id='elasticpress-related-posts-block-css' href='https://cacm.acm.org/wp-content/mu-plugins/search/elasticpress/dist/css/related-posts-block-styles.min.css?ver=4.2.2' type='text/css' media='all' /> <style id='global-styles-inline-css' type='text/css'> :root{--wp--preset--aspect-ratio--square: 1;--wp--preset--aspect-ratio--4-3: 4/3;--wp--preset--aspect-ratio--3-4: 3/4;--wp--preset--aspect-ratio--3-2: 3/2;--wp--preset--aspect-ratio--2-3: 2/3;--wp--preset--aspect-ratio--16-9: 16/9;--wp--preset--aspect-ratio--9-16: 9/16;--wp--preset--color--black: #000000;--wp--preset--color--cyan-bluish-gray: #abb8c3;--wp--preset--color--white: #ffffff;--wp--preset--color--pale-pink: #f78da7;--wp--preset--color--vivid-red: #cf2e2e;--wp--preset--color--luminous-vivid-orange: #ff6900;--wp--preset--color--luminous-vivid-amber: #fcb900;--wp--preset--color--light-green-cyan: #7bdcb5;--wp--preset--color--vivid-green-cyan: #00d084;--wp--preset--color--pale-cyan-blue: #8ed1fc;--wp--preset--color--vivid-cyan-blue: #0693e3;--wp--preset--color--vivid-purple: #9b51e0;--wp--preset--color--cacm-blue: #337AB5;--wp--preset--color--cacm-link-blue: #015FAC;--wp--preset--color--cacm-dark-blue: #1E4A88;--wp--preset--color--cacm-darker-blue: #29303C;--wp--preset--color--cacm-light-blue: #B6DEFF;--wp--preset--color--cacm-peach: #F7ACA5;--wp--preset--color--cacm-beige: #F5F2DC;--wp--preset--color--cacm-brown: #8C6A54;--wp--preset--color--cacm-green: #5F7D05;--wp--preset--color--cacm-light-green: #EFF7F1;--wp--preset--color--cacm-black: #141414;--wp--preset--color--cacm-gray-100: #FBFCFC;--wp--preset--color--cacm-gray-200: #F8F9FA;--wp--preset--color--cacm-gray-300: #EBEDEF;--wp--preset--color--cacm-gray-500: #A9ACB1;--wp--preset--color--cacm-gray-600: #5A6875;--wp--preset--color--cacm-gray-700: #3D4550;--wp--preset--gradient--vivid-cyan-blue-to-vivid-purple: linear-gradient(135deg,rgba(6,147,227,1) 0%,rgb(155,81,224) 100%);--wp--preset--gradient--light-green-cyan-to-vivid-green-cyan: linear-gradient(135deg,rgb(122,220,180) 0%,rgb(0,208,130) 100%);--wp--preset--gradient--luminous-vivid-amber-to-luminous-vivid-orange: linear-gradient(135deg,rgba(252,185,0,1) 0%,rgba(255,105,0,1) 100%);--wp--preset--gradient--luminous-vivid-orange-to-vivid-red: linear-gradient(135deg,rgba(255,105,0,1) 0%,rgb(207,46,46) 100%);--wp--preset--gradient--very-light-gray-to-cyan-bluish-gray: linear-gradient(135deg,rgb(238,238,238) 0%,rgb(169,184,195) 100%);--wp--preset--gradient--cool-to-warm-spectrum: linear-gradient(135deg,rgb(74,234,220) 0%,rgb(151,120,209) 20%,rgb(207,42,186) 40%,rgb(238,44,130) 60%,rgb(251,105,98) 80%,rgb(254,248,76) 100%);--wp--preset--gradient--blush-light-purple: linear-gradient(135deg,rgb(255,206,236) 0%,rgb(152,150,240) 100%);--wp--preset--gradient--blush-bordeaux: linear-gradient(135deg,rgb(254,205,165) 0%,rgb(254,45,45) 50%,rgb(107,0,62) 100%);--wp--preset--gradient--luminous-dusk: linear-gradient(135deg,rgb(255,203,112) 0%,rgb(199,81,192) 50%,rgb(65,88,208) 100%);--wp--preset--gradient--pale-ocean: linear-gradient(135deg,rgb(255,245,203) 0%,rgb(182,227,212) 50%,rgb(51,167,181) 100%);--wp--preset--gradient--electric-grass: linear-gradient(135deg,rgb(202,248,128) 0%,rgb(113,206,126) 100%);--wp--preset--gradient--midnight: linear-gradient(135deg,rgb(2,3,129) 0%,rgb(40,116,252) 100%);--wp--preset--gradient--primary-gradient: linear-gradient(90deg, #80C2EF 0%, #337AB5 100%);--wp--preset--font-size--small: 13px;--wp--preset--font-size--medium: 20px;--wp--preset--font-size--large: 36px;--wp--preset--font-size--x-large: 42px;--wp--preset--font-size--work-xxxs: 16px;--wp--preset--font-size--work-xxs: 18px;--wp--preset--font-size--work-xs: 21px;--wp--preset--font-size--work-sm: 25px;--wp--preset--font-size--work-md: 28px;--wp--preset--font-size--work-lg: 33px;--wp--preset--font-size--work-xl: 37px;--wp--preset--font-size--work-xxl: 41px;--wp--preset--font-size--work-xxxl: 48px;--wp--preset--font-size--inter-xxxs: 15px;--wp--preset--font-size--inter-xxs: 18px;--wp--preset--font-size--inter-xs: 21px;--wp--preset--font-size--inter-sm: 24px;--wp--preset--font-size--inter-md: 28px;--wp--preset--font-size--inter-lg: 32px;--wp--preset--font-size--inter-xl: 36px;--wp--preset--font-size--inter-xxl: 41px;--wp--preset--font-size--inter-xxxl: 47px;--wp--preset--font-family--inter: 'Inter', helvetica, arial, sans-serif;--wp--preset--font-family--work-sans: 'Work Sans', helvetica, arial, sans-serif;--wp--preset--spacing--20: 0.44rem;--wp--preset--spacing--30: 0.67rem;--wp--preset--spacing--40: 1rem;--wp--preset--spacing--50: 1.5rem;--wp--preset--spacing--60: 2.25rem;--wp--preset--spacing--70: 3.38rem;--wp--preset--spacing--80: 5.06rem;--wp--preset--shadow--natural: 6px 6px 9px rgba(0, 0, 0, 0.2);--wp--preset--shadow--deep: 12px 12px 50px rgba(0, 0, 0, 0.4);--wp--preset--shadow--sharp: 6px 6px 0px rgba(0, 0, 0, 0.2);--wp--preset--shadow--outlined: 6px 6px 0px -3px rgba(255, 255, 255, 1), 6px 6px rgba(0, 0, 0, 1);--wp--preset--shadow--crisp: 6px 6px 0px rgba(0, 0, 0, 1);--wp--custom--adminbar-height: 0px;--wp--custom--siteheader-height: 72px;--wp--custom--site-edge: 20px;--wp--custom--gap: 40px;--wp--custom--gap-half: calc(var(--wp--custom--gap) / 2);--wp--custom--section-background-color: transparent;--wp--custom--placeholder-background-color: var(--wp--preset--color--cacm-gray-200);--wp--custom--vertical-block-rhythm: 40px;--wp--custom--border-gray: 1px solid var(--wp--preset--color--cacm-gray-300);--wp--custom--font-weight-regular: 400;--wp--custom--font-weight-medium: 500;--wp--custom--font-weight-bold: 700;--wp--custom--font-weight-extrabold: 900;}.wp-block-heading{--wp--preset--font-size--work-xxs: 18px;--wp--preset--font-size--work-xs: 21px;--wp--preset--font-size--work-sm: 25px;--wp--preset--font-size--work-md: 28px;--wp--preset--font-size--work-lg: 33px;--wp--preset--font-size--work-xl: 41px;}:root { --wp--style--global--content-size: 1280px;--wp--style--global--wide-size: 1280px; }:where(body) { margin: 0; }.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }.wp-site-blocks > .alignright { float: right; margin-left: 2em; }.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }:where(.is-layout-flex){gap: 0.5em;}:where(.is-layout-grid){gap: 0.5em;}.is-layout-flow > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-flow > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-flow > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignleft{float: left;margin-inline-start: 0;margin-inline-end: 2em;}.is-layout-constrained > .alignright{float: right;margin-inline-start: 2em;margin-inline-end: 0;}.is-layout-constrained > .aligncenter{margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > :where(:not(.alignleft):not(.alignright):not(.alignfull)){max-width: var(--wp--style--global--content-size);margin-left: auto !important;margin-right: auto !important;}.is-layout-constrained > .alignwide{max-width: var(--wp--style--global--wide-size);}body .is-layout-flex{display: flex;}.is-layout-flex{flex-wrap: wrap;align-items: center;}.is-layout-flex > :is(*, div){margin: 0;}body .is-layout-grid{display: grid;}.is-layout-grid > :is(*, div){margin: 0;}body{padding-top: 0px;padding-right: 0px;padding-bottom: 0px;padding-left: 0px;}a:where(:not(.wp-element-button)){text-decoration: underline;}:root :where(.wp-element-button, .wp-block-button__link){background-color: #32373c;border-width: 0;color: #fff;font-family: inherit;font-size: inherit;line-height: inherit;padding: calc(0.667em + 2px) calc(1.333em + 2px);text-decoration: none;}.has-black-color{color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-color{color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-color{color: var(--wp--preset--color--white) !important;}.has-pale-pink-color{color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-color{color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-color{color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-color{color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-color{color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-color{color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-color{color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-color{color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-color{color: var(--wp--preset--color--vivid-purple) !important;}.has-cacm-blue-color{color: var(--wp--preset--color--cacm-blue) !important;}.has-cacm-link-blue-color{color: var(--wp--preset--color--cacm-link-blue) !important;}.has-cacm-dark-blue-color{color: var(--wp--preset--color--cacm-dark-blue) !important;}.has-cacm-darker-blue-color{color: var(--wp--preset--color--cacm-darker-blue) !important;}.has-cacm-light-blue-color{color: var(--wp--preset--color--cacm-light-blue) !important;}.has-cacm-peach-color{color: var(--wp--preset--color--cacm-peach) !important;}.has-cacm-beige-color{color: var(--wp--preset--color--cacm-beige) !important;}.has-cacm-brown-color{color: var(--wp--preset--color--cacm-brown) !important;}.has-cacm-green-color{color: var(--wp--preset--color--cacm-green) !important;}.has-cacm-light-green-color{color: var(--wp--preset--color--cacm-light-green) !important;}.has-cacm-black-color{color: var(--wp--preset--color--cacm-black) !important;}.has-cacm-gray-100-color{color: var(--wp--preset--color--cacm-gray-100) !important;}.has-cacm-gray-200-color{color: var(--wp--preset--color--cacm-gray-200) !important;}.has-cacm-gray-300-color{color: var(--wp--preset--color--cacm-gray-300) !important;}.has-cacm-gray-500-color{color: var(--wp--preset--color--cacm-gray-500) !important;}.has-cacm-gray-600-color{color: var(--wp--preset--color--cacm-gray-600) !important;}.has-cacm-gray-700-color{color: var(--wp--preset--color--cacm-gray-700) !important;}.has-black-background-color{background-color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-background-color{background-color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-background-color{background-color: var(--wp--preset--color--white) !important;}.has-pale-pink-background-color{background-color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-background-color{background-color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-background-color{background-color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-background-color{background-color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-background-color{background-color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-background-color{background-color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-background-color{background-color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-background-color{background-color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-background-color{background-color: var(--wp--preset--color--vivid-purple) !important;}.has-cacm-blue-background-color{background-color: var(--wp--preset--color--cacm-blue) !important;}.has-cacm-link-blue-background-color{background-color: var(--wp--preset--color--cacm-link-blue) !important;}.has-cacm-dark-blue-background-color{background-color: var(--wp--preset--color--cacm-dark-blue) !important;}.has-cacm-darker-blue-background-color{background-color: var(--wp--preset--color--cacm-darker-blue) !important;}.has-cacm-light-blue-background-color{background-color: var(--wp--preset--color--cacm-light-blue) !important;}.has-cacm-peach-background-color{background-color: var(--wp--preset--color--cacm-peach) !important;}.has-cacm-beige-background-color{background-color: var(--wp--preset--color--cacm-beige) !important;}.has-cacm-brown-background-color{background-color: var(--wp--preset--color--cacm-brown) !important;}.has-cacm-green-background-color{background-color: var(--wp--preset--color--cacm-green) !important;}.has-cacm-light-green-background-color{background-color: var(--wp--preset--color--cacm-light-green) !important;}.has-cacm-black-background-color{background-color: var(--wp--preset--color--cacm-black) !important;}.has-cacm-gray-100-background-color{background-color: var(--wp--preset--color--cacm-gray-100) !important;}.has-cacm-gray-200-background-color{background-color: var(--wp--preset--color--cacm-gray-200) !important;}.has-cacm-gray-300-background-color{background-color: var(--wp--preset--color--cacm-gray-300) !important;}.has-cacm-gray-500-background-color{background-color: var(--wp--preset--color--cacm-gray-500) !important;}.has-cacm-gray-600-background-color{background-color: var(--wp--preset--color--cacm-gray-600) !important;}.has-cacm-gray-700-background-color{background-color: var(--wp--preset--color--cacm-gray-700) !important;}.has-black-border-color{border-color: var(--wp--preset--color--black) !important;}.has-cyan-bluish-gray-border-color{border-color: var(--wp--preset--color--cyan-bluish-gray) !important;}.has-white-border-color{border-color: var(--wp--preset--color--white) !important;}.has-pale-pink-border-color{border-color: var(--wp--preset--color--pale-pink) !important;}.has-vivid-red-border-color{border-color: var(--wp--preset--color--vivid-red) !important;}.has-luminous-vivid-orange-border-color{border-color: var(--wp--preset--color--luminous-vivid-orange) !important;}.has-luminous-vivid-amber-border-color{border-color: var(--wp--preset--color--luminous-vivid-amber) !important;}.has-light-green-cyan-border-color{border-color: var(--wp--preset--color--light-green-cyan) !important;}.has-vivid-green-cyan-border-color{border-color: var(--wp--preset--color--vivid-green-cyan) !important;}.has-pale-cyan-blue-border-color{border-color: var(--wp--preset--color--pale-cyan-blue) !important;}.has-vivid-cyan-blue-border-color{border-color: var(--wp--preset--color--vivid-cyan-blue) !important;}.has-vivid-purple-border-color{border-color: var(--wp--preset--color--vivid-purple) !important;}.has-cacm-blue-border-color{border-color: var(--wp--preset--color--cacm-blue) !important;}.has-cacm-link-blue-border-color{border-color: var(--wp--preset--color--cacm-link-blue) !important;}.has-cacm-dark-blue-border-color{border-color: var(--wp--preset--color--cacm-dark-blue) !important;}.has-cacm-darker-blue-border-color{border-color: var(--wp--preset--color--cacm-darker-blue) !important;}.has-cacm-light-blue-border-color{border-color: var(--wp--preset--color--cacm-light-blue) !important;}.has-cacm-peach-border-color{border-color: var(--wp--preset--color--cacm-peach) !important;}.has-cacm-beige-border-color{border-color: var(--wp--preset--color--cacm-beige) !important;}.has-cacm-brown-border-color{border-color: var(--wp--preset--color--cacm-brown) !important;}.has-cacm-green-border-color{border-color: var(--wp--preset--color--cacm-green) !important;}.has-cacm-light-green-border-color{border-color: var(--wp--preset--color--cacm-light-green) !important;}.has-cacm-black-border-color{border-color: var(--wp--preset--color--cacm-black) !important;}.has-cacm-gray-100-border-color{border-color: var(--wp--preset--color--cacm-gray-100) !important;}.has-cacm-gray-200-border-color{border-color: var(--wp--preset--color--cacm-gray-200) !important;}.has-cacm-gray-300-border-color{border-color: var(--wp--preset--color--cacm-gray-300) !important;}.has-cacm-gray-500-border-color{border-color: var(--wp--preset--color--cacm-gray-500) !important;}.has-cacm-gray-600-border-color{border-color: var(--wp--preset--color--cacm-gray-600) !important;}.has-cacm-gray-700-border-color{border-color: var(--wp--preset--color--cacm-gray-700) !important;}.has-vivid-cyan-blue-to-vivid-purple-gradient-background{background: var(--wp--preset--gradient--vivid-cyan-blue-to-vivid-purple) !important;}.has-light-green-cyan-to-vivid-green-cyan-gradient-background{background: var(--wp--preset--gradient--light-green-cyan-to-vivid-green-cyan) !important;}.has-luminous-vivid-amber-to-luminous-vivid-orange-gradient-background{background: var(--wp--preset--gradient--luminous-vivid-amber-to-luminous-vivid-orange) !important;}.has-luminous-vivid-orange-to-vivid-red-gradient-background{background: var(--wp--preset--gradient--luminous-vivid-orange-to-vivid-red) !important;}.has-very-light-gray-to-cyan-bluish-gray-gradient-background{background: var(--wp--preset--gradient--very-light-gray-to-cyan-bluish-gray) !important;}.has-cool-to-warm-spectrum-gradient-background{background: var(--wp--preset--gradient--cool-to-warm-spectrum) !important;}.has-blush-light-purple-gradient-background{background: var(--wp--preset--gradient--blush-light-purple) !important;}.has-blush-bordeaux-gradient-background{background: var(--wp--preset--gradient--blush-bordeaux) !important;}.has-luminous-dusk-gradient-background{background: var(--wp--preset--gradient--luminous-dusk) !important;}.has-pale-ocean-gradient-background{background: var(--wp--preset--gradient--pale-ocean) !important;}.has-electric-grass-gradient-background{background: var(--wp--preset--gradient--electric-grass) !important;}.has-midnight-gradient-background{background: var(--wp--preset--gradient--midnight) !important;}.has-primary-gradient-gradient-background{background: var(--wp--preset--gradient--primary-gradient) !important;}.has-small-font-size{font-size: var(--wp--preset--font-size--small) !important;}.has-medium-font-size{font-size: var(--wp--preset--font-size--medium) !important;}.has-large-font-size{font-size: var(--wp--preset--font-size--large) !important;}.has-x-large-font-size{font-size: var(--wp--preset--font-size--x-large) !important;}.has-work-xxxs-font-size{font-size: var(--wp--preset--font-size--work-xxxs) !important;}.has-work-xxs-font-size{font-size: var(--wp--preset--font-size--work-xxs) !important;}.has-work-xs-font-size{font-size: var(--wp--preset--font-size--work-xs) !important;}.has-work-sm-font-size{font-size: var(--wp--preset--font-size--work-sm) !important;}.has-work-md-font-size{font-size: var(--wp--preset--font-size--work-md) !important;}.has-work-lg-font-size{font-size: var(--wp--preset--font-size--work-lg) !important;}.has-work-xl-font-size{font-size: var(--wp--preset--font-size--work-xl) !important;}.has-work-xxl-font-size{font-size: var(--wp--preset--font-size--work-xxl) !important;}.has-work-xxxl-font-size{font-size: var(--wp--preset--font-size--work-xxxl) !important;}.has-inter-xxxs-font-size{font-size: var(--wp--preset--font-size--inter-xxxs) !important;}.has-inter-xxs-font-size{font-size: var(--wp--preset--font-size--inter-xxs) !important;}.has-inter-xs-font-size{font-size: var(--wp--preset--font-size--inter-xs) !important;}.has-inter-sm-font-size{font-size: var(--wp--preset--font-size--inter-sm) !important;}.has-inter-md-font-size{font-size: var(--wp--preset--font-size--inter-md) !important;}.has-inter-lg-font-size{font-size: var(--wp--preset--font-size--inter-lg) !important;}.has-inter-xl-font-size{font-size: var(--wp--preset--font-size--inter-xl) !important;}.has-inter-xxl-font-size{font-size: var(--wp--preset--font-size--inter-xxl) !important;}.has-inter-xxxl-font-size{font-size: var(--wp--preset--font-size--inter-xxxl) !important;}.has-inter-font-family{font-family: var(--wp--preset--font-family--inter) !important;}.has-work-sans-font-family{font-family: var(--wp--preset--font-family--work-sans) !important;}.wp-block-heading.has-work-xxs-font-size{font-size: var(--wp--preset--font-size--work-xxs) !important;}.wp-block-heading.has-work-xs-font-size{font-size: var(--wp--preset--font-size--work-xs) !important;}.wp-block-heading.has-work-sm-font-size{font-size: var(--wp--preset--font-size--work-sm) !important;}.wp-block-heading.has-work-md-font-size{font-size: var(--wp--preset--font-size--work-md) !important;}.wp-block-heading.has-work-lg-font-size{font-size: var(--wp--preset--font-size--work-lg) !important;}.wp-block-heading.has-work-xl-font-size{font-size: var(--wp--preset--font-size--work-xl) !important;} :where(.wp-block-post-template.is-layout-flex){gap: 1.25em;}:where(.wp-block-post-template.is-layout-grid){gap: 1.25em;} :where(.wp-block-columns.is-layout-flex){gap: 2em;}:where(.wp-block-columns.is-layout-grid){gap: 2em;} :root :where(.wp-block-pullquote){font-size: 1.5em;line-height: 1.6;} </style> <link rel='stylesheet' id='qm-object-cache-style-css' href='https://cacm.acm.org/wp-content/mu-plugins/qm-plugins/qm-object-cache/css/style.css?ver=0.2' type='text/css' media='all' /> <link rel='stylesheet' id='cacm-global-css' href='https://cacm.acm.org/wp-content/themes/cacm/client/build/css/global.min.css?ver=6f460684b3d49b0b7b10' type='text/css' media='all' /> <link rel='stylesheet' id='cacm-article-css' href='https://cacm.acm.org/wp-content/themes/cacm/client/build/css/article.min.css?ver=34500f5fcb3e83888a6c' type='text/css' media='all' /> <link rel="https://api.w.org/" href="https://cacm.acm.org/wp-json/" /><link rel="alternate" title="JSON" type="application/json" href="https://cacm.acm.org/wp-json/wp/v2/digital-library/758290" /><link rel="EditURI" type="application/rsd+xml" title="RSD" href="https://cacm.acm.org/xmlrpc.php?rsd" /> <meta name="generator" content="WordPress 6.7.1" /> <link rel="canonical" href="https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/" /> <link rel='shortlink' href='https://cacm.acm.org/?p=758290' /> <link rel="alternate" title="oEmbed (JSON)" type="application/json+oembed" href="https://cacm.acm.org/wp-json/oembed/1.0/embed?url=https%3A%2F%2Fcacm.acm.org%2Flatin-america-regional-special-section%2Frecent-advances-on-principles-of-concurrent-data-structures%2F" /> <link rel="alternate" title="oEmbed (XML)" type="text/xml+oembed" href="https://cacm.acm.org/wp-json/oembed/1.0/embed?url=https%3A%2F%2Fcacm.acm.org%2Flatin-america-regional-special-section%2Frecent-advances-on-principles-of-concurrent-data-structures%2F&format=xml" /> <style> .getty.aligncenter { text-align: center; } .getty.alignleft { float: none; margin-right: 0; } .getty.alignleft > div { float: left; margin-right: 5px; } .getty.alignright { float: none; margin-left: 0; } .getty.alignright > div { float: right; margin-left: 5px; } </style> <style>img#wpstats{display:none}</style> <link rel="icon" href="https://cacm.acm.org/wp-content/uploads/2023/11/cropped-cropped-cacm_favicon-1.png?w=32" sizes="32x32" /> <link rel="icon" href="https://cacm.acm.org/wp-content/uploads/2023/11/cropped-cropped-cacm_favicon-1.png?w=192" sizes="192x192" /> <link rel="apple-touch-icon" href="https://cacm.acm.org/wp-content/uploads/2023/11/cropped-cropped-cacm_favicon-1.png?w=180" /> <meta name="msapplication-TileImage" content="https://cacm.acm.org/wp-content/uploads/2023/11/cropped-cropped-cacm_favicon-1.png?w=270" /> </head> <body class="digital-library-template-default single single-digital-library postid-758290"> <svg xmlns="http://www.w3.org/2000/svg" focusable="false" height="0" role="none" style="left:-9999px;overflow:hidden;position:absolute" viewBox="0 0 0 0" width="0"><symbol id="am-symbol-icon-arrow-left" viewBox="0 0 18 12"><path clip-rule="evenodd" d="M18 6a.643.643 0 0 1-.643.643H2.196l4.046 4.044a.644.644 0 0 1-.91.91L.188 6.456a.643.643 0 0 1 0-.91L5.33.402a.644.644 0 1 1 .91.91L2.197 5.358h15.161A.643.643 0 0 1 18 6Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-arrow-right" viewBox="0 0 14 9"><path clip-rule="evenodd" d="M0 4.5A.5.5 0 0 1 .5 4h11.793L9.146.854a.5.5 0 1 1 .708-.708l4 4a.5.5 0 0 1 0 .708l-4 4a.5.5 0 1 1-.708-.708L12.293 5H.5a.5.5 0 0 1-.5-.5Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-comment" viewBox="0 0 19 20"><path clip-rule="evenodd" d="M1.781 1.542a.693.693 0 0 0-.693.693v11.876a.693.693 0 0 0 .693.693h2.375c.273 0 .494.221.494.494v2.574l3.96-2.97a.494.494 0 0 1 .296-.098h8.313a.693.693 0 0 0 .693-.694V2.236a.693.693 0 0 0-.693-.693H1.78ZM.592 1.046a1.681 1.681 0 0 1 1.19-.492h15.437A1.681 1.681 0 0 1 18.9 2.235v11.876a1.681 1.681 0 0 1-1.681 1.681H9.07l-4.618 3.464a.494.494 0 0 1-.79-.396v-3.068H1.78A1.682 1.682 0 0 1 .1 14.111V2.235c0-.446.177-.873.492-1.189Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-digital-library" viewBox="43 0 40 40"><g clip-path="url(#a)"> <path d="m95.468 15.585-1.58 1.579c-.262.263-.584.41-.964.41h-6.813V4.707h6.813c.38 0 .702.146.965.409l1.579 1.579c.263.263.41.585.41.965v6.959c0 .38-.118.702-.41.965zm-1.9-7.544c0-.088-.03-.205-.118-.263l-.76-.76c-.088-.088-.146-.117-.263-.117H88.42v8.45h4.006c.117 0 .205-.03.263-.117l.76-.76a.357.357 0 0 0 .117-.264V8.04zm5.877 9.532v-2.047h2.309V6.754h-2.31V4.708h6.93v2.046h-2.31v8.772h2.31v2.047h-6.93zm19.853 0-.292-1.637-1.228 1.228c-.263.263-.585.41-.965.41h-3.918c-.38 0-.702-.147-.965-.41l-1.579-1.58a1.326 1.326 0 0 1-.409-.964V7.66c0-.38.146-.7.409-.964l1.579-1.579c.263-.263.585-.41.965-.41h5c.38 0 .701.147.965.41l1.666 1.667-1.549 1.55-1.316-1.316c-.088-.088-.146-.117-.263-.117h-4.006c-.117 0-.205.029-.263.117l-.761.76a.36.36 0 0 0-.117.263v6.199c0 .088.03.204.117.263l.761.76c.087.088.146.117.263.117h3.041c.117 0 .204-.03.263-.117l1.754-1.754c.088-.088.117-.146.117-.263v-.995h-3.187V10.06h5.497v4.97l.497 2.573h-2.076v-.029zm5.38 0v-2.047h2.31V6.754h-2.31V4.708h6.93v2.046h-2.31v8.772h2.31v2.047h-6.93zM140.029 6.9v10.644h-2.31V6.9h-3.713V4.708h9.737V6.9h-3.714zm14.299 10.673-1.229-3.216h-5.117l-1.228 3.216h-2.31l4.767-12.865h2.748l4.708 12.865h-2.339zm-3.772-10.38-1.784 5.088h3.567l-1.783-5.088zM160 17.573V4.708h2.31V15.35h6.316v2.193H160v.03zM86.111 35.41V22.543h2.31v10.643h6.316v2.193H86.11v.03zm11.813 0v-2.047h2.31V24.59h-2.31v-2.047h6.93v2.047h-2.31v8.772h2.31v2.046h-6.93zm20.497-1.638-1.257 1.257a1.28 1.28 0 0 1-.936.38h-7.164V22.544h7.164c.38 0 .673.146.936.38l1.257 1.257c.263.263.409.585.409.965v1.755c0 .38-.146.701-.409.965l-1.111 1.11 1.111 1.112c.263.263.409.584.409.965v1.783c0 .322-.146.673-.409.936zm-1.901-8.216c0-.117-.029-.205-.116-.264l-.439-.438c-.088-.088-.146-.117-.263-.117h-4.328v3.129h3.86c.088 0 .205-.03.263-.117l.877-.878c.088-.087.117-.146.117-.263v-1.052h.029zm0 5.789c0-.117-.029-.205-.116-.263l-.936-.936c-.088-.088-.146-.117-.263-.117h-3.831v3.158h4.328c.087 0 .204-.03.263-.117l.439-.438c.087-.088.116-.147.116-.264v-1.023zm14.65 4.065-3.802-4.884a.402.402 0 0 0-.321-.175h-1.404v5.058h-2.31V22.544h7.164c.38 0 .673.146.936.38l1.257 1.257c.263.263.409.585.409.965v2.544c0 .38-.146.702-.409.965l-1.257 1.257c-.263.263-.556.38-.936.38h-.468l3.977 5.059h-2.836v.058zm-.381-9.854c0-.117-.029-.205-.116-.264l-.439-.438c-.088-.088-.146-.117-.263-.117h-4.328v3.392h4.328c.117 0 .204-.03.263-.117l.439-.41c.087-.087.116-.146.116-.263v-1.783zm15.117 9.854-1.228-3.217h-5.117l-1.228 3.216h-2.31l4.766-12.865h2.749l4.708 12.865h-2.34zm-3.772-10.38-1.783 5.087h3.538l-1.755-5.088zm17.106 10.38-3.801-4.884a.405.405 0 0 0-.322-.175h-1.404v5.058h-2.309V22.544h7.163c.38 0 .673.146.936.38l1.257 1.257c.263.263.41.585.41.965v2.544c0 .38-.147.702-.41.965l-1.257 1.257c-.263.263-.556.38-.936.38h-.468l3.977 5.059h-2.836v.058zm-.41-9.854c0-.117-.029-.205-.117-.264l-.438-.438c-.088-.088-.146-.117-.263-.117h-4.328v3.392h4.328c.117 0 .204-.03.263-.117l.438-.41c.088-.087.117-.146.117-.263v-1.783zm11.696 4.152v5.672h-2.31v-5.672l-4.356-7.164h2.514l3.012 5 2.982-5h2.486l-4.328 7.164zM12.193 26.199 7.485 13.363H4.737L0 26.199h2.31l1.199-3.216h5.117l1.199 3.216h2.368zm-4.327-5.263h-3.54l1.784-5.088 1.755 5.088zm15.818 3.187-1.55-1.55-1.315 1.316c-.088.088-.146.117-.263.117h-3.188c-.116 0-.204-.03-.263-.117l-.76-.76a.357.357 0 0 1-.117-.264v-6.17c0-.087.03-.204.117-.262l.76-.76c.088-.088.146-.117.263-.117h3.188c.116 0 .204.029.263.117l1.316 1.315 1.55-1.55-1.668-1.666a1.326 1.326 0 0 0-.964-.41H16.87c-.38 0-.701.147-.965.41l-1.579 1.579a1.326 1.326 0 0 0-.409.965v6.959c0 .38.146.702.41.965l1.578 1.579c.264.263.585.41.965.41h4.182c.38 0 .701-.147.964-.41l1.667-1.696zm15.79 2.076V13.363h-3.538l-3.041 9.941-3.041-9.941h-3.538v12.836h2.251V15.994L31.696 26.2h2.398l3.128-10.205V26.2h2.252zM58.246 3.421l-5.351-1.403-1.404 5.35 3.86-1.052 2.895-2.895zm-4.474 4.532-7.72 2.106 1.17 4.385 6.55-6.49zm26.17 6.988 1.432-5.467-5.35-1.375 1.081 4.065 2.837 2.777zm-33.1 10.205-1.433 5.38 5.351 1.375-1.052-3.89-2.866-2.865zM73.333 2.66 68.89 3.89l6.579 6.579-2.135-7.807zm-.409 29.416 7.836-2.134-1.228-4.474-6.608 6.608zM68.45 36.55l5.468 1.433 1.404-5.351-4.065 1.081-2.807 2.837zm-15 .79 4.386-1.17-6.462-6.492 2.076 7.661zm26.2-13.656L83.332 20 71.637 8.304l-4.561-4.561L63.333 0l-6.52 6.52-9.708 9.708L43.333 20l6.58 6.579 9.707 9.707L63.333 40l6.492-6.491 9.824-9.825zm-16.434-.643c0 .35-.117.672-.38.906l-1.491 1.492c-.263.263-.556.38-.906.38h-6.462V13.626h6.462c.35 0 .672.117.906.38l1.491 1.491c.263.263.38.556.38.907v6.637zm3.597-9.415h2.193v10.117H75v2.076h-8.187V13.626z"></path> <path d="M60.205 15.819a.37.37 0 0 0-.264-.117h-3.8v8.04h3.8c.117 0 .176-.029.264-.116l.701-.702c.059-.088.117-.175.117-.263v-5.877a.357.357 0 0 0-.117-.264l-.701-.701z"></path> </g><defs> <clipPath id="a"> <path d="M0 0h174.854v40H0z"></path> </clipPath> </defs></symbol><symbol id="am-symbol-icon-pdf-download" viewBox="0 0 19 20"><path clip-rule="evenodd" d="M1.781 1.542a.693.693 0 0 0-.693.693v13.063a.693.693 0 0 0 .693.694h4.75a.494.494 0 1 1 0 .988h-4.75A1.682 1.682 0 0 1 .1 15.298V2.235A1.681 1.681 0 0 1 1.78.554h8.415c.446 0 .873.177 1.188.492l2.274 2.274c.315.315.492.743.492 1.188v2.477a.494.494 0 1 1-.988 0V4.508a.694.694 0 0 0-.203-.49m0 0-2.273-2.273a.694.694 0 0 0-.49-.203H1.78m11.875 8.312a4.256 4.256 0 1 0 0 8.512 4.256 4.256 0 0 0 0-8.512Zm-5.244 4.257a5.244 5.244 0 1 1 10.488 0 5.244 5.244 0 0 1-10.488 0Zm5.244-2.87c.273 0 .494.222.494.495v3.557l.938-.938a.494.494 0 0 1 .699.698l-1.782 1.782a.494.494 0 0 1-.698 0l-1.781-1.782a.494.494 0 0 1 .698-.698l.938.938v-3.557c0-.273.221-.495.494-.495Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-print" viewBox="0 0 19 20"><path clip-rule="evenodd" d="M5.344 1.541a.693.693 0 0 0-.694.693v3.069h9.7V2.234a.693.693 0 0 0-.694-.693H5.344Zm9.994 3.762V2.234A1.681 1.681 0 0 0 13.656.553H5.344a1.681 1.681 0 0 0-1.682 1.681v3.069h-1.88A1.682 1.682 0 0 0 .1 6.984v5.938a1.682 1.682 0 0 0 1.681 1.681h1.881v4.257c0 .272.221.494.494.494h10.688a.494.494 0 0 0 .494-.494v-4.256h1.88a1.682 1.682 0 0 0 1.682-1.682V6.984a1.681 1.681 0 0 0-1.681-1.681h-1.881ZM1.78 6.291a.693.693 0 0 0-.693.693v5.938a.694.694 0 0 0 .693.694h1.881v-3.069c0-.273.221-.494.494-.494h10.688c.273 0 .494.221.494.494v3.069h1.88a.694.694 0 0 0 .694-.694V6.984a.693.693 0 0 0-.693-.693H1.78Zm12.569 4.75h-9.7v7.325h9.7V11.04ZM2.475 8.172c0-.273.22-.494.494-.494h1.187a.494.494 0 1 1 0 .988H2.97a.494.494 0 0 1-.494-.494Zm3.562 4.75c0-.273.221-.494.494-.494h5.938a.494.494 0 1 1 0 .988H6.53a.494.494 0 0 1-.494-.494Zm0 2.375c0-.273.221-.494.494-.494h4.157a.494.494 0 1 1 0 .988H6.53a.494.494 0 0 1-.494-.494Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-share" viewBox="0 0 19 18"><path clip-rule="evenodd" d="M14.844 1.73a2.475 2.475 0 1 0 0 4.949 2.475 2.475 0 0 0 0-4.95ZM11.38 4.203a3.463 3.463 0 1 1 .447 1.703L7.531 7.58a3.473 3.473 0 0 1-.087 1.873l4.555 2.278a3.463 3.463 0 1 1-.442.883L7 10.335a3.463 3.463 0 1 1 .171-3.677l4.298-1.671a3.473 3.473 0 0 1-.089-.783Zm1.242 8.407a2.475 2.475 0 1 0 4.441 2.187 2.475 2.475 0 0 0-4.44-2.187ZM4.156 5.886a2.475 2.475 0 1 0 0 4.95 2.475 2.475 0 0 0 0-4.95Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-bookmark" viewBox="0 0 13 19"><path clip-rule="evenodd" d="M12.05.948c-.293-.32-.7-.494-1.114-.494H2.007c-.421 0-.821.175-1.121.494a1.73 1.73 0 0 0-.457 1.186v15.488c0 .198.05.388.142.563.1.167.236.304.408.395a.89.89 0 0 0 .535.122.956.956 0 0 0 .522-.19l2.464-1.84h.007l1.964-1.459 1.958 1.46h.014l2.464 1.839c.15.114.329.182.522.19a.89.89 0 0 0 .535-.122 1.03 1.03 0 0 0 .4-.395c.1-.175.15-.365.15-.563V2.134c0-.449-.164-.874-.464-1.186ZM3.771 16.011 1.5 17.7s-.029.015-.05.022c-.014 0-.029-.007-.043-.015-.021-.008-.028-.023-.043-.038-.007-.015-.007-.03-.007-.053V2.134a.74.74 0 0 1 .186-.494.639.639 0 0 1 .464-.198h1.764v14.57Zm4.465-.691-1.5-1.125a.462.462 0 0 0-.536 0L4.7 15.32V1.442h3.536V15.32Zm3.35 2.378v-.053s-.015.015-.015.023a.089.089 0 0 1-.035.038c-.015 0-.036.015-.05.015-.015-.007-.036-.007-.05-.023l-2.272-1.687V1.442h1.772c.171 0 .335.069.457.198a.747.747 0 0 1 .193.494v15.564Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-bookmarked" viewBox="0 0 17 25"><path clip-rule="evenodd" d="M16.27.65C15.86.23 15.29 0 14.71 0H2.21A2.201 2.201 0 0 0 0 2.21v20.38c0 .26.07.51.2.74.14.22.33.4.57.52.23.13.49.18.75.16.26-.01.51-.1.73-.25l3.45-2.42h.01l1.15-.8 1.6-1.12 1.6 1.12 1.14.8h.02l3.45 2.42c.21.15.46.24.73.25.26.02.52-.03.75-.16.23-.12.43-.3.56-.52.14-.23.21-.48.21-.74V2.21c0-.59-.23-1.15-.65-1.56ZM4.68 20.47 1.5 22.69s-.04.02-.07.03c-.02 0-.04-.01-.06-.02-.03-.01-.04-.03-.06-.05V2.21c0-.24.09-.47.26-.65.17-.17.41-.26.65-.26h2.47v19.17h-.01Zm10.94 2.22v-.07s-.02.02-.02.03a.12.12 0 0 1-.05.05c-.02 0-.05.02-.07.02-.02-.01-.05-.01-.07-.03l-3.18-2.22V1.3h2.48a.9.9 0 0 1 .64.26c.17.18.27.41.27.65v20.48Z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-chevron-down" viewBox="0 0 16 16"><path d="M1.646 4.646a.5.5 0 0 1 .708 0L8 10.293l5.646-5.647a.5.5 0 0 1 .708.708l-6 6a.5.5 0 0 1-.708 0l-6-6a.5.5 0 0 1 0-.708z" fill-rule="evenodd"></path></symbol><symbol id="am-symbol-icon-search" viewBox="0 0 24 24"><path d="m23 21.85-6.145-6.146a8.966 8.966 0 1 0-1.151 1.15L21.849 23 23 21.85ZM2.656 9.98a7.324 7.324 0 1 1 7.324 7.324A7.332 7.332 0 0 1 2.656 9.98Z" fill="#015FAC"></path></symbol><symbol id="am-symbol-cacm-logo-small"><path d="M48.75 24c0 13.255-10.745 24-24 24s-24-10.745-24-24 10.745-24 24-24 24 10.745 24 24Z" fill="#fff"></path><path d="m24.998 9-15 15 15 15 15-15-15-15Z" fill="#027BA3"></path><path d="M34.196 24A9.195 9.195 0 0 1 25 33.196 9.195 9.195 0 0 1 15.804 24 9.195 9.195 0 0 1 25 14.804 9.195 9.195 0 0 1 34.196 24Z" fill="#fff"></path><path d="M33.28 24A8.275 8.275 0 0 1 25 32.275 8.275 8.275 0 0 1 16.72 24c0-4.57 3.705-8.28 8.28-8.28A8.276 8.276 0 0 1 33.28 24Z" fill="#027BA3"></path><path d="M20.18 25.613c-.084.07-.163.133-.23.191a1.641 1.641 0 0 1-.596.292c-.104.025-.25.041-.441.041-.35 0-.642-.116-.875-.354a1.219 1.219 0 0 1-.35-.891c0-.296.058-.534.175-.717.116-.183.287-.325.508-.433.225-.109.492-.184.804-.225.313-.042.646-.075 1.004-.1v-.021c0-.221-.083-.371-.241-.454-.163-.084-.405-.125-.73-.125-.145 0-.316.025-.512.079s-.388.12-.571.204h-.104v-.967c.12-.037.32-.079.596-.125.275-.05.55-.075.829-.075.687 0 1.187.117 1.5.342.312.23.47.575.47 1.046v2.712h-1.241v-.42h.004Zm0-.621v-.825c-.21.02-.38.041-.505.054-.13.017-.258.046-.38.091a.561.561 0 0 0-.253.171.488.488 0 0 0-.088.305c0 .187.05.312.15.383.1.07.246.104.442.104a.802.802 0 0 0 .329-.075c.113-.05.212-.12.304-.208ZM24.154 26.137c-.329 0-.633-.041-.904-.125a1.897 1.897 0 0 1-.712-.383c-.2-.17-.355-.387-.467-.65a2.336 2.336 0 0 1-.167-.925c0-.379.058-.704.183-.97.121-.267.284-.488.492-.659.2-.167.433-.288.7-.367a2.98 2.98 0 0 1 1.504-.046c.221.05.442.134.667.242v1.067h-.158c-.05-.046-.113-.1-.184-.154a1.673 1.673 0 0 0-.237-.159 1.349 1.349 0 0 0-.683-.175c-.317 0-.563.109-.738.33-.175.22-.262.516-.262.891 0 .4.091.696.279.892.187.196.433.296.741.296.155 0 .296-.017.413-.055a1.27 1.27 0 0 0 .517-.28c.058-.049.112-.099.154-.14h.158v1.062l-.246.108a2.925 2.925 0 0 1-.629.175 2.776 2.776 0 0 1-.417.026h-.004ZM30.867 26.033v-1.991c0-.196 0-.363-.013-.496a1.102 1.102 0 0 0-.062-.33.386.386 0 0 0-.167-.187.715.715 0 0 0-.317-.058.665.665 0 0 0-.279.062 1.99 1.99 0 0 0-.304.175v2.83h-1.242v-1.992c0-.192 0-.358-.012-.496a1 1 0 0 0-.067-.333.386.386 0 0 0-.166-.188.707.707 0 0 0-.313-.058c-.1 0-.2.025-.3.07-.096.05-.192.105-.283.167v2.83H26.1v-3.984h1.242v.438c.204-.175.396-.309.575-.405a1.27 1.27 0 0 1 .604-.145c.246 0 .458.058.642.175.183.116.325.287.42.516.238-.22.467-.391.675-.512.213-.121.425-.18.642-.18.183 0 .35.03.496.088.146.058.27.146.37.267.113.129.197.279.25.454.055.175.084.408.084.692v2.596h-1.242l.009-.005Z" fill="#fff"></path></symbol><symbol id="am-symbol-cacm-logo" viewBox="30.79 34.55 548.86 88.05"><path d="M54.75 71.41c-.8.8-1.77 1.2-2.85 1.2H39.52c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85v-20.6c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2H51.9c1.08 0 2.05.4 2.85 1.2l4.96 4.96-4.62 4.56-3.88-3.88c-.23-.23-.46-.34-.8-.34H41c-.34 0-.57.11-.8.34l-2.23 2.23c-.23.23-.34.51-.34.8v18.31c0 .29.11.57.34.8l2.23 2.23c.23.23.46.34.8.34h9.41c.34 0 .57-.11.8-.34l3.88-3.88 4.62 4.56-4.96 4.97zm44.5-4.68-4.68 4.68c-.8.8-1.77 1.2-2.85 1.2H76.83c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85v-20.6c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2h14.89c1.08 0 2.05.4 2.85 1.2l4.68 4.68c.8.8 1.2 1.77 1.2 2.85v20.6c0 1.08-.4 2.05-1.2 2.85zM93.6 44.42c0-.29-.11-.57-.34-.8l-2.23-2.23c-.23-.23-.46-.34-.8-.34H78.31c-.34 0-.57.11-.8.34l-2.23 2.23c-.23.23-.34.51-.34.8v18.31c0 .29.11.57.34.8l2.23 2.23c.23.23.46.34.8.34h11.92c.34 0 .57-.11.8-.34l2.23-2.23c.23-.23.34-.51.34-.8V44.42zm50.44 28.19V42.37l-9.3 30.24h-7.07l-9.3-30.24v30.24h-6.68V34.55h10.5l9.01 29.5 9.01-29.5h10.5V72.6h-6.67zm52.65 0V42.37l-9.3 30.24h-7.07l-9.3-30.24v30.24h-6.68V34.55h10.5l9.01 29.5 9.01-29.5h10.5V72.6h-6.67zm46.66-5.88-4.68 4.68c-.8.8-1.77 1.2-2.85 1.2h-11.47c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85V34.55h6.85v28.18c0 .29.11.57.34.8l2.23 2.23c.23.23.46.34.8.34h8.5c.34 0 .57-.11.8-.34l2.23-2.23c.23-.23.34-.51.34-.8V34.55h6.85v29.33c-.01 1.08-.41 2.05-1.21 2.85zm32.69 5.88-12.55-29.5v29.5h-6.67V34.55h9.7l12.55 29.5v-29.5h6.67V72.6h-9.7zm20.82 0v-6.05h6.85V40.6h-6.85v-6.05h20.54v6.05h-6.85v25.96h6.85v6.05h-20.54zm53.46-1.2c-.8.8-1.77 1.2-2.85 1.2h-12.38c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85v-20.6c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2h12.38c1.08 0 2.05.4 2.85 1.2l4.96 4.96-4.62 4.56-3.88-3.88c-.23-.23-.46-.34-.8-.34h-9.41c-.34 0-.57.11-.8.34l-2.22 2.23c-.23.23-.34.51-.34.8v18.31c0 .29.11.57.34.8l2.22 2.23c.23.23.46.34.8.34h9.41c.34 0 .57-.11.8-.34l3.88-3.88 4.62 4.56-4.96 4.97zm39.47 1.2-3.59-9.53h-15.18l-3.6 9.53h-6.85l14.09-38.05h8.1l13.98 38.05h-6.95zm-11.18-30.7-5.25 15.06h10.5l-5.25-15.06zm35.94-.85v31.55h-6.85V41.06h-11.01v-6.5h28.87v6.5h-11.01zm19.27 31.55v-6.05h6.85V40.6h-6.85v-6.05h20.54v6.05h-6.85v25.96h6.85v6.05h-20.54zm61.89-5.88-4.68 4.68c-.8.8-1.77 1.2-2.85 1.2h-14.89c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85v-20.6c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2h14.89c1.08 0 2.05.4 2.85 1.2l4.68 4.68c.8.8 1.2 1.77 1.2 2.85v20.6c0 1.08-.4 2.05-1.2 2.85zm-5.64-22.31c0-.29-.11-.57-.34-.8l-2.22-2.23c-.23-.23-.46-.34-.8-.34h-11.92c-.34 0-.57.11-.8.34l-2.22 2.23c-.23.23-.34.51-.34.8v18.31c0 .29.12.57.34.8l2.22 2.23c.23.23.46.34.8.34h11.92c.34 0 .57-.11.8-.34l2.22-2.23c.23-.23.34-.51.34-.8V44.42zm37.65 28.19-12.55-29.5v29.5h-6.68V34.55h9.7l12.55 29.5v-29.5h6.68V72.6h-9.7zm50.72-5.88-4.68 4.68c-.8.8-1.77 1.2-2.85 1.2h-15.92c-1.08 0-2.05-.4-2.85-1.2l-4.85-4.85 4.56-4.62 3.82 3.82c.23.23.46.34.8.34h12.95c.34 0 .57-.11.8-.34l2.22-2.23c.23-.23.34-.51.34-.8v-3.65c0-.57-.51-1.08-1.08-1.14l-20.48-2.74c-2.23-.29-3.94-2.28-3.94-4.45v-7.47c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2h15.92c1.08 0 2.05.4 2.85 1.2l4.85 4.85-4.56 4.62-3.82-3.82c-.23-.23-.46-.34-.8-.34H557.5c-.34 0-.57.11-.8.34l-2.22 2.23c-.23.23-.34.51-.34.8v3.65c0 .57.46 1.08 1.03 1.14l20.54 2.74c2.22.29 3.94 2.28 3.94 4.45v7.47c-.01 1.08-.41 2.05-1.21 2.85zM263.05 90.51l-.88.88c-.15.15-.33.22-.54.22h-2.79a.79.79 0 0 1-.54-.22l-.88-.88a.732.732 0 0 1-.22-.54v-3.86c0-.2.07-.38.22-.54l.88-.88c.15-.15.33-.22.54-.22h2.79c.2 0 .39.07.54.22l.88.88c.15.15.22.33.22.54v3.86c0 .2-.07.39-.22.54zm-1.06-4.19a.22.22 0 0 0-.06-.15l-.42-.42a.204.204 0 0 0-.15-.06h-2.24c-.06 0-.11.02-.15.06l-.42.42a.22.22 0 0 0-.06.15v3.43c0 .05.02.11.06.15l.42.42c.04.04.09.06.15.06h2.24c.06 0 .11-.02.15-.06l.42-.42c.04-.04.06-.1.06-.15v-3.43zm5.41 2.33v2.96h-1.28v-7.13h4.78v1.22h-3.5v1.73h3.5v1.22h-3.5zm12.04-2.96v5.92h-1.28v-5.92h-2.06v-1.22h5.41v1.22h-2.07zm8.45 5.92v-2.96h-2.86v2.96h-1.28v-7.13h1.28v2.95h2.86v-2.95h1.28v7.13h-1.28zm4.43 0v-7.13h4.78v1.22h-3.5v1.73h3.5v1.22h-3.5v1.74h3.5v1.22h-4.78zm30.16 30.99-3.59-9.53h-15.18l-3.59 9.53h-6.85l14.09-38.05h8.1l13.98 38.05h-6.96zM311.3 91.91l-5.25 15.06h10.5l-5.25-15.06zm49.12 29.49c-.8.8-1.77 1.2-2.85 1.2h-12.38c-1.08 0-2.05-.4-2.85-1.2l-4.68-4.68c-.8-.8-1.2-1.77-1.2-2.85v-20.6c0-1.08.4-2.05 1.2-2.85l4.68-4.68c.8-.8 1.77-1.2 2.85-1.2h12.38c1.08 0 2.05.4 2.85 1.2l4.96 4.96-4.62 4.56-3.88-3.88c-.23-.23-.46-.34-.8-.34h-9.41c-.34 0-.57.11-.8.34l-2.22 2.23c-.23.23-.34.51-.34.8v18.31c0 .29.12.57.34.8l2.22 2.23c.23.23.46.34.8.34h9.41c.34 0 .57-.12.8-.34l3.88-3.88 4.62 4.56-4.96 4.97zm47.51 1.2V92.36l-9.3 30.24h-7.07l-9.3-30.24v30.24h-6.68V84.55h10.5l9.01 29.5 9.01-29.5h10.5v38.05h-6.67z"></path></symbol><symbol id="am-symbol-icon-social-facebook"><path d="m22.723 20 .445-2.896h-2.779v-1.879c0-.792.388-1.564 1.633-1.564h1.263v-2.465S22.139 11 21.043 11c-2.289 0-3.784 1.387-3.784 3.898v2.206h-2.544V20h2.544v7h3.13v-7h2.334Z"></path></symbol><symbol id="am-symbol-icon-social-twitter"><path d="M27.613 13.657a7.057 7.057 0 0 1-2.03.557 3.54 3.54 0 0 0 1.555-1.955 7.08 7.08 0 0 1-2.245.857A3.53 3.53 0 0 0 22.313 12c-2.282 0-3.958 2.13-3.442 4.34a10.033 10.033 0 0 1-7.285-3.694 3.54 3.54 0 0 0 1.093 4.72 3.52 3.52 0 0 1-1.6-.442c-.038 1.637 1.135 3.169 2.835 3.51a3.542 3.542 0 0 1-1.596.06 3.538 3.538 0 0 0 3.301 2.454 7.106 7.106 0 0 1-5.232 1.465A10.006 10.006 0 0 0 15.804 26c6.562 0 10.27-5.542 10.046-10.513a7.195 7.195 0 0 0 1.763-1.83Z"></path></symbol><symbol id="am-symbol-icon-social-linkedin"><path d="M14.117 12.74c0 .96-.773 1.738-1.726 1.738a1.732 1.732 0 0 1-1.725-1.739c0-.96.772-1.739 1.725-1.739.953 0 1.726.78 1.726 1.74Zm.013 3.13h-3.478V27h3.479V15.87Zm5.553 0h-3.456V27h3.457v-5.843c0-3.248 4.194-3.514 4.194 0V27h3.47v-7.048c0-5.481-6.207-5.282-7.665-2.583v-1.5Z"></path></symbol><symbol id="am-symbol-icon-social-reddit"><path d="M27.764 21.071v.613c0 3.368-3.879 6.022-8.676 6.022-4.797 0-8.676-2.654-8.676-6.022v-.613c-1.122-.51-1.53-1.735-1.122-2.857.306-.817 1.123-1.327 1.939-1.225.612 0 1.123.204 1.531.612 1.735-1.122 3.776-1.837 5.818-1.837l1.122-5.103c0-.102.102-.204.102-.204.102-.102.205-.102.307-.102l3.572.816c.408-.714 1.327-1.123 2.041-.714.715.408 1.123 1.326.715 2.04-.409.715-1.327 1.124-2.042.715-.51-.204-.816-.714-.816-1.326l-3.164-.715-1.02 4.593c2.245.102 4.286.817 5.715 1.837.816-.816 2.245-.816 3.062 0 .408.408.612.919.612 1.531.306.919-.306 1.633-1.02 1.94Zm-11.942 1.123c.816 0 1.53-.714 1.53-1.53 0-.817-.714-1.532-1.53-1.532-.817 0-1.531.715-1.531 1.531 0 .817.612 1.531 1.53 1.531Zm7.042 1.94c-.204-.205-.408-.205-.51 0-.612.714-2.041.918-3.062.918-1.02 0-2.45-.204-3.062-.919-.204-.204-.408-.204-.51 0-.204.204-.204.409 0 .51 1.02 1.021 3.062 1.123 3.674 1.123.613 0 2.552-.102 3.675-1.122-.102-.102-.102-.306-.205-.51Zm1.225-3.47c0-.817-.714-1.532-1.53-1.532-.817 0-1.532.715-1.532 1.531 0 .817.715 1.531 1.531 1.531.817 0 1.531-.714 1.531-1.53Z"></path></symbol><symbol id="am-symbol-cacm-avatar-blank" viewBox="0 0 40 40"><g> <circle cx="20" cy="20" fill="var(--wp--preset--color--cacm-link-blue)" r="19" stroke="var(--wp--preset--color--cacm-link-blue)" stroke-width="2"></circle> <path clip-rule="evenodd" d="M5 33.23v-.73c0-4.987 9.994-7.5 15-7.5s15 2.513 15 7.5v.73A19.952 19.952 0 0 1 20 40a19.952 19.952 0 0 1-15-6.77ZM20 8.333a7.498 7.498 0 0 0-7.5 7.5c0 4.143 3.356 7.5 7.5 7.5s7.5-3.357 7.5-7.5c0-4.144-3.356-7.5-7.5-7.5Z" fill="var(--wp--preset--color--cacm-gray-200)" fill-rule="evenodd"></path> </g></symbol></svg><div id="page" class="site"> <a class="skip-link" href="#content">Skip to content</a> <div class="site-header-wrapper" data-component="siteHeader"> <header id="masthead" class="site-header site-header--no-js"> <div class="site-header-container"> <button class="site-header-hamburger" aria-label="Main Menu"> <span class="site-header-hamburger-closed"> <svg xmlns="http://www.w3.org/2000/svg" version="1.2" viewBox="0 0 25 25"> <path d="M.2.2h24.6v2.6H.2zm0 11h24.6v2.7H.2zm0 11h24.6v2.6H.2z" style="fill:#1a1a1a"/> </svg> </span> <span class="site-header-hamburger-open"> <svg xmlns="http://www.w3.org/2000/svg" version="1.2" viewBox="0 0 25 25"> <path d="M1.7.9 24 23.8m-23 0L23.3.9" style="fill:none;stroke:#fff;stroke-width:1.3"/> </svg> </span> </button> <a class="site-header-logo" aria-label="Home" href="https://cacm.acm.org"> <svg aria-hidden="true" focusable="false" width="548" height="88" fill="#000"><use href="#am-symbol-cacm-logo"></use></svg> <svg aria-hidden="true" focusable="false" width="548" height="88" fill="#FFF"><use href="#am-symbol-cacm-logo"></use></svg> </a> <div class="site-header-topics-menu"> <button class="site-header-topics-menu-toggle"> Explore Topics <svg xmlns="http://www.w3.org/2000/svg" width="14" height="8" fill="none"> <path stroke="#1A1A1A" stroke-width="1.5" d="m1.5 1.5 5.5 5 5.5-5"/> </svg> </button> <nav role="navigation" aria-label="Topics Menu" class="site-header-topics-menu-expanded" aria-hidden="true"> <ul class="site-header-topics-menu-list"> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/architecture-and-hardware/"> Architecture and Hardware </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/"> Artificial Intelligence and Machine Learning </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/computer-history/"> Computer History </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/computing-applications/"> Computing Applications </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/computing-profession/"> Computing Profession </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/data-and-information/"> Data and Information </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/education/"> Education </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/hci/"> HCI </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/philosophy-of-computing/"> Philosophy of Computing </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/security-and-privacy/"> Security and Privacy </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/society/"> Society </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/software-engineering-and-programming-languages/"> Software Engineering and Programming Languages </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/systems-and-networking/"> Systems and Networking </a> </li> <li class="site-header-topics-menu-list-item"> <a href="https://cacm.acm.org/category/theory/"> Theory </a> </li> </ul> </nav> </div> <div class="site-header-magazine-menu"> <button class="site-header-magazine-menu-toggle"> Latest Issue <svg xmlns="http://www.w3.org/2000/svg" width="14" height="8" fill="none"> <path stroke="#1A1A1A" stroke-width="1.5" d="m1.5 1.5 5.5 5 5.5-5"/> </svg> </button> <nav role="navigation" aria-label="Magazine Menu" class="site-header-magazine-menu-expanded" aria-hidden="true"> <a href="https://cacm.acm.org/issue/december-2024/"> <figure class="site-header-magazine-menu-expanded-image"> <div class="image-wrapper"><img width="1000" height="1338" src="https://cacm.acm.org/wp-content/uploads/2024/11/Dec.2024-Cover-1000x1338-1.jpg?w=1000" class="attachment-original size-original" alt="December 2024 CACM cover" loading="lazy" decoding="async" srcset="https://cacm.acm.org/wp-content/uploads/2024/11/Dec.2024-Cover-1000x1338-1.jpg 1000w, https://cacm.acm.org/wp-content/uploads/2024/11/Dec.2024-Cover-1000x1338-1.jpg?resize=224,300 224w, https://cacm.acm.org/wp-content/uploads/2024/11/Dec.2024-Cover-1000x1338-1.jpg?resize=768,1028 768w, https://cacm.acm.org/wp-content/uploads/2024/11/Dec.2024-Cover-1000x1338-1.jpg?resize=765,1024 765w" sizes="auto, (max-width: 1000px) 100vw, 1000px" /></div> </figure> </a> <div class="site-header-magazine-menu-expanded-text"> <div class="site-header-magazine-menu-expanded-current"> <h2 class="site-header-magazine-menu-expanded-heading"> Latest Issue </h2> <a href="https://cacm.acm.org/issue/december-2024/" class="site-header-magazine-menu-expanded-issue"><b>December 2024</b>, Vol. 67 No. 12</a> </div> <div class="site-header-magazine-menu-expanded-previous"> <h2 class="site-header-magazine-menu-expanded-heading"> Previous Issue </h2> <a href="https://cacm.acm.org/issue/november-2024/" class="site-header-magazine-menu-expanded-issue"><b>November 2024</b>, Vol. 67 No. 11</a> </div> <a href="https://cacm.acm.org/issues" class="site-header-magazine-menu-expanded-link"> Explore the archive <svg xmlns="http://www.w3.org/2000/svg" width="12" height="10" fill="none" aria-hidden="true" tabindex="-1"> <path fill="#000" d="m7 0-.715.697 3.79 3.803H0v1h10.075l-3.79 3.787L7 10l5-5-5-5Z"/> </svg> </a> </div> </nav> </div> <a href="https://cacm.acm.org/?s=" aria-label="Search" class="site-header-search"> <span class="site-header-search-text"> Search </span> <svg aria-hidden="true" focusable="false" width="24" height="24" class="site-header-search-icon"><use href="#am-symbol-icon-search"></use></svg></a> <nav class="site-header-membership-nav"> <button class="site-header-membership-nav__button"> <span class="site-header-membership-nav__button-text">Open Membership Navigation</span> <span class="site-header-membership-nav__button-icon"> <svg aria-hidden="true" focusable="false" width="40" height="40" tabindex="-1"><use href="#am-symbol-cacm-avatar-blank"></use></svg> </span> </button> <div class="site-header-membership-nav__menu-container" aria-hidden="true"> <ul class="site-header-membership-nav__menu"> <li class="site-header-membership-nav__menu-item"> <a href="https://cacm.acm.org/account/settings">Settings</a> </li> <li class="site-header-membership-nav__menu-item"> <a href="https://cacm.acm.org/logout/">Sign Out</a> </li> </ul> </div> </nav> <a class="site-header-member-login-link" href="https://cacm.acm.org/wp-login.php?saml_sso">Sign In</a> <a href="https://cacm.acm.org/join-acm" class="site-header-cta-membership"> <div class="site-header-cta-membership-container"> <div class="site-header-cta-membership-text"> Join ACM <svg xmlns="http://www.w3.org/2000/svg" width="12" height="10" fill="none" aria-hidden="true" tabindex="-1"> <path fill="#000" d="m7 0-.715.697 3.79 3.803H0v1h10.075l-3.79 3.787L7 10l5-5-5-5Z"/> </svg> </div> <div class="site-header-cta-membership-logo"> <svg aria-hidden="true" focusable="false" width="48" height="48"><use href="#am-symbol-cacm-logo-small"></use></svg> </div> </div> </a> </div> <nav role="navigation" aria-label="Main Menu" class="site-header-hamburger-menu" aria-hidden="true">  <form role="search" action="https://cacm.acm.org" method="get" class="site-header-hamburger-menu-search"> <label for="site-navigation-expanded-search"> <span class="site-header-hamburger-menu-search-icon"> <svg xmlns="http://www.w3.org/2000/svg" width="21" height="21" fill="none"> <path fill="#4C4C4C" d="m21 19.902-5.866-5.867a8.558 8.558 0 1 0-1.099 1.099L19.902 21 21 19.902ZM1.581 8.572a6.99 6.99 0 1 1 6.99 6.99 6.999 6.999 0 0 1-6.99-6.99Z"/> </svg> </span> <input type="text" name="s" id="site-navigation-expanded-search" class="site-header-hamburger-menu-search-input" placeholder="Search" value="" /> </label> </form>  <div class="site-header-hamburger-menu-topics site-header-hamburger-menu-topics--expanded"> <h2 class="site-header-hamburger-menu-heading"> Topics <span class="site-header-hamburger-menu-accordion-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </h2> <ul class="site-header-hamburger-menu-topics-menu"> <li> <a href="https://cacm.acm.org/category/architecture-and-hardware/"> Architecture and Hardware </a> </li> <li> <a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/"> Artificial Intelligence and Machine Learning </a> </li> <li> <a href="https://cacm.acm.org/category/computer-history/"> Computer History </a> </li> <li> <a href="https://cacm.acm.org/category/computing-applications/"> Computing Applications </a> </li> <li> <a href="https://cacm.acm.org/category/computing-profession/"> Computing Profession </a> </li> <li> <a href="https://cacm.acm.org/category/data-and-information/"> Data and Information </a> </li> <li> <a href="https://cacm.acm.org/category/education/"> Education </a> </li> <li> <a href="https://cacm.acm.org/category/hci/"> HCI </a> </li> <li> <a href="https://cacm.acm.org/category/philosophy-of-computing/"> Philosophy of Computing </a> </li> <li> <a href="https://cacm.acm.org/category/security-and-privacy/"> Security and Privacy </a> </li> <li> <a href="https://cacm.acm.org/category/society/"> Society </a> </li> <li> <a href="https://cacm.acm.org/category/software-engineering-and-programming-languages/"> Software Engineering and Programming Languages </a> </li> <li> <a href="https://cacm.acm.org/category/systems-and-networking/"> Systems and Networking </a> </li> <li> <a href="https://cacm.acm.org/category/theory/"> Theory </a> </li> </ul> </div>  <div class="site-header-hamburger-menu-sections"> <h2 class="site-header-hamburger-menu-heading"> Sections <span class="site-header-hamburger-menu-accordion-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </h2> <ul class="site-header-hamburger-menu-sections-menu"> <li> <a href="https://cacm.acm.org/section/research/"> Research and Advances </a> </li> <li> <a href="https://cacm.acm.org/section/opinion/"> Opinion </a> </li> <li> <a href="https://cacm.acm.org/section/practice/"> Practice </a> </li> <li> <a href="https://cacm.acm.org/section/news/"> News </a> </li> <li> <a href="https://cacm.acm.org/section/careers/"> Careers </a> </li> </ul> </div>  <div class="site-header-hamburger-menu-magazine"> <h2 class="site-header-hamburger-menu-heading"> Magazine <span class="site-header-hamburger-menu-accordion-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </h2> <ul id="menu-magazine-header" class="site-header-hamburger-menu-magazine-menu"><li id="menu-item-217988" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217988"><a href="/issue/latest/" id="menu-link-1">Latest Issue</a></li> <li id="menu-item-217989" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217989"><a href="/issues/" id="menu-link-2">Magazine Archive</a></li> <li id="menu-item-224644" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224644"><a href="https://cacm.acm.org/editorial-staff-board/" id="menu-link-3">Editorial Staff and Board</a></li> <li id="menu-item-751386" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-751386"><a href="https://cacm.acm.org/author-guidelines#CACMsubmission" id="menu-link-4">Submit an Article</a></li> <li id="menu-item-224585" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224585"><a href="https://cacm.acm.org/feeds-2/" id="menu-link-5">Alerts & Feeds</a></li> <li id="menu-item-224645" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224645"><a href="https://cacm.acm.org/author-guidelines/" id="menu-link-6">Author Guidelines</a></li> </ul> </div> <div class="site-header-hamburger-menu-membership"> <span class="site-header-hamburger-menu-membership-logo"> <svg aria-hidden="true" focusable="false" width="49" height="48"><use href="#am-symbol-cacm-logo-small"></use></svg> </span> <h2 class="site-header-hamburger-menu-heading site-header-hamburger-menu-membership-heading"> CACM Web Account </h2> <p class="site-header-hamburger-menu-membership-text">Membership in ACM includes a subscription to Communications of the ACM (CACM), the computing industry's most trusted source for staying connected to the world of advanced computing.</p> <div class="site-header-hamburger-menu-membership-buttons"> <a href="https://cacm.acm.org/wp-login.php?saml_sso" class="site-header-hamburger-menu-membership-buttons-log-in"> Sign In </a> <a href="https://accounts.acm.org/" class="site-header-hamburger-menu-membership-buttons-sign-up"> Sign Up </a> </div> </div>  <div class="site-header-hamburger-menu-communications"> <h2 class="site-header-hamburger-menu-heading"> Communications of the ACM <span class="site-header-hamburger-menu-accordion-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </h2> <ul id="menu-communications-header" class="site-header-hamburger-menu-communications-menu"><li id="menu-item-224641" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224641"><a href="https://cacm.acm.org/about-us/" id="menu-link-7">About Us</a></li> <li id="menu-item-224663" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224663"><a href="https://cacm.acm.org/faq/" id="menu-link-8">Frequently Asked Questions</a></li> <li id="menu-item-224640" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224640"><a href="https://cacm.acm.org/contact-us/" id="menu-link-9">Contact Us</a></li> </ul> </div> <div class="site-header-hamburger-menu-social"> <h2 class="site-header-hamburger-menu-heading"> Follow Us </h2> <ul class="site-header-hamburger-menu-social-menu"> <li> <a href="https://twitter.com/cacmmag"> <span class="screen-reader-only">CACM on Twitter</span> <svg xmlns="http://www.w3.org/2000/svg" width="38" height="38" fill="none"> <path fill="#1DA1F2" d="M27.613 13.657a7.057 7.057 0 0 1-2.03.557 3.54 3.54 0 0 0 1.555-1.955 7.08 7.08 0 0 1-2.245.857A3.53 3.53 0 0 0 22.313 12c-2.282 0-3.958 2.13-3.442 4.34a10.033 10.033 0 0 1-7.285-3.694 3.54 3.54 0 0 0 1.093 4.72 3.52 3.52 0 0 1-1.6-.442c-.038 1.637 1.135 3.169 2.835 3.51a3.542 3.542 0 0 1-1.596.06 3.538 3.538 0 0 0 3.301 2.454 7.106 7.106 0 0 1-5.232 1.465A10.006 10.006 0 0 0 15.804 26c6.562 0 10.27-5.542 10.046-10.513a7.195 7.195 0 0 0 1.763-1.83Z"/> <path fill="#000" d="M27.613 13.657a7.057 7.057 0 0 1-2.03.557 3.54 3.54 0 0 0 1.555-1.955 7.08 7.08 0 0 1-2.245.857A3.53 3.53 0 0 0 22.313 12c-2.282 0-3.958 2.13-3.442 4.34a10.033 10.033 0 0 1-7.285-3.694 3.54 3.54 0 0 0 1.093 4.72 3.52 3.52 0 0 1-1.6-.442c-.038 1.637 1.135 3.169 2.835 3.51a3.542 3.542 0 0 1-1.596.06 3.538 3.538 0 0 0 3.301 2.454 7.106 7.106 0 0 1-5.232 1.465A10.006 10.006 0 0 0 15.804 26c6.562 0 10.27-5.542 10.046-10.513a7.195 7.195 0 0 0 1.763-1.83Z"/> <rect width="37" height="37" x=".5" y=".5" stroke="#D8D8D8" rx="18.5"/> </svg> </a> </li> <li> <a href="https://www.reddit.com/user/TheOfficialACM"> <span class="screen-reader-only">CACM on Reddit</span> <svg xmlns="http://www.w3.org/2000/svg" width="38" height="38" fill="none"> <path fill="#FF4500" d="M27.764 21.071v.613c0 3.368-3.879 6.022-8.676 6.022-4.797 0-8.676-2.654-8.676-6.022v-.613c-1.122-.51-1.53-1.735-1.122-2.857.306-.817 1.123-1.327 1.939-1.225.612 0 1.123.204 1.531.612 1.735-1.122 3.776-1.837 5.818-1.837l1.122-5.103c0-.102.102-.204.102-.204.102-.102.205-.102.307-.102l3.572.816c.408-.714 1.327-1.123 2.041-.714.715.408 1.123 1.326.715 2.04-.409.715-1.327 1.124-2.042.715-.51-.204-.816-.714-.816-1.326l-3.164-.715-1.02 4.593c2.245.102 4.286.817 5.715 1.837.816-.816 2.245-.816 3.062 0 .408.408.612.919.612 1.531.306.919-.306 1.633-1.02 1.94Zm-11.942 1.123c.816 0 1.53-.714 1.53-1.53 0-.817-.714-1.532-1.53-1.532-.817 0-1.531.715-1.531 1.531 0 .817.612 1.531 1.53 1.531Zm7.042 1.94c-.204-.205-.408-.205-.51 0-.612.714-2.041.918-3.062.918-1.02 0-2.45-.204-3.062-.919-.204-.204-.408-.204-.51 0-.204.204-.204.409 0 .51 1.02 1.021 3.062 1.123 3.674 1.123.613 0 2.552-.102 3.675-1.122-.102-.102-.102-.306-.205-.51Zm1.225-3.47c0-.817-.714-1.532-1.53-1.532-.817 0-1.532.715-1.532 1.531 0 .817.715 1.531 1.531 1.531.817 0 1.531-.714 1.531-1.53Z"/> <path fill="#000" d="M27.764 21.071v.613c0 3.368-3.879 6.022-8.676 6.022-4.797 0-8.676-2.654-8.676-6.022v-.613c-1.122-.51-1.53-1.735-1.122-2.857.306-.817 1.123-1.327 1.939-1.225.612 0 1.123.204 1.531.612 1.735-1.122 3.776-1.837 5.818-1.837l1.122-5.103c0-.102.102-.204.102-.204.102-.102.205-.102.307-.102l3.572.816c.408-.714 1.327-1.123 2.041-.714.715.408 1.123 1.326.715 2.04-.409.715-1.327 1.124-2.042.715-.51-.204-.816-.714-.816-1.326l-3.164-.715-1.02 4.593c2.245.102 4.286.817 5.715 1.837.816-.816 2.245-.816 3.062 0 .408.408.612.919.612 1.531.306.919-.306 1.633-1.02 1.94Zm-11.942 1.123c.816 0 1.53-.714 1.53-1.53 0-.817-.714-1.532-1.53-1.532-.817 0-1.531.715-1.531 1.531 0 .817.612 1.531 1.53 1.531Zm7.042 1.94c-.204-.205-.408-.205-.51 0-.612.714-2.041.918-3.062.918-1.02 0-2.45-.204-3.062-.919-.204-.204-.408-.204-.51 0-.204.204-.204.409 0 .51 1.02 1.021 3.062 1.123 3.674 1.123.613 0 2.552-.102 3.675-1.122-.102-.102-.102-.306-.205-.51Zm1.225-3.47c0-.817-.714-1.532-1.53-1.532-.817 0-1.532.715-1.532 1.531 0 .817.715 1.531 1.531 1.531.817 0 1.531-.714 1.531-1.53Z"/> <rect width="37" height="37" x=".5" y=".5" stroke="#D8D8D8" rx="18.5"/> </svg> </a> </li> <li> <a href="https://www.linkedin.com/groups/36836/"> <span class="screen-reader-only">CACM on LinkedIn</span> <svg xmlns="http://www.w3.org/2000/svg" width="38" height="38" fill="none"> <path fill="#000" d="M14.117 12.74c0 .96-.773 1.738-1.726 1.738a1.732 1.732 0 0 1-1.725-1.739c0-.96.772-1.739 1.725-1.739.953 0 1.726.78 1.726 1.74Zm.013 3.13h-3.478V27h3.479V15.87Zm5.553 0h-3.456V27h3.457v-5.843c0-3.248 4.194-3.514 4.194 0V27h3.47v-7.048c0-5.481-6.207-5.282-7.665-2.583v-1.5Z"/> <rect width="37" height="37" x=".5" y=".5" stroke="#D8D8D8" rx="18.5"/> </svg> </a> </li> </ul> </div> </nav> </header> </div> <div id="content" class="site-content container"> <div id="primary" class="content-area"> <main id="main" class="site-main"> <article id="post-758290" class="post-758290 digital-library type-digital-library status-publish has-post-thumbnail hentry category-data-and-information category-software-engineering-and-programming-languages issue-august-2024 section-latin-america-regional-special-section"> <header class="article-header article-header--default"> <div class="article-header__inner container"> <div class="article-header__section"><a href="https://cacm.acm.org/section/latin-america-regional-special-section/">Latin America Regional Special Section</a></div> <div class="article-header__topic-and-issue-section"> <span class="article-header__topic"> <a href="https://cacm.acm.org/category/data-and-information/">Data and Information</a> </span> <span class="article-header__issue-section"> </span> </div> <h1 class="article-header__title">Recent Advances on Principles of Concurrent Data Structures</h1> <div class="article-header__subtitle"><p>Concurrent data structures are a key factor in exploiting the inherent parallelism of modern multicore architectures.</p> </div> <div class="article-header__meta"> <div class="article-header__byline"> By <a href="https://cacm.acm.org/author/armando-castaneda/" title="Posts by Armando Castañeda" class="author url fn" rel="author">Armando Castañeda</a> and <a href="https://cacm.acm.org/author/sergio-rajsbaum/" title="Posts by Sergio Rajsbaum" class="author url fn" rel="author">Sergio Rajsbaum</a> </div> <div class="article-header__posted-on"> <span class="posted-on">Posted <time datetime="2024-07-11T16:41:54-04:00">Jul 11 2024</time></span> </div> </div> <figure class="article-header__figure"> <div class="image-wrapper image-wrapper--widescreen"><img width="1024" height="576" src="https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg" class="attachment-full size-full" alt="rows of colored lights in space, illustration" loading="eager" decoding="async" srcset="https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg 2400w, https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg?resize=300,169 300w, https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg?resize=768,432 768w, https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg?resize=1024,576 1024w, https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg?resize=1536,864 1536w, https://cacm.acm.org/wp-content/uploads/2024/07/071524.RSS_.Recent-Advances.jpg?resize=2048,1152 2048w" sizes="(max-width: 1024px) 100vw, 1024px" /></div> </figure> <div class="article-header__share"> <ul class="share"> <li class="share-link" data-component="share"> <a href="#" class="share-toggle"> <svg aria-hidden="true" focusable="false" width="19" height="18" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-share"></use></svg> <span class="share-link-text"> Share </span> </a> <ul class="share-menu" aria-hidden="true"> <li> <a href="https://twitter.com/intent/tweet?url=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&text=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Twitter </a> </li> <li> <a href="http://www.reddit.com/submit?url=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&title=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Reddit </a> </li> <li> <a href="https://news.ycombinator.com/submitlink?u=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&t=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Hacker News </a> </li> </ul> </li> <li class="share-link share-link-pdf"> <a href="https://dl.acm.org/doi/pdf/10.1145/3653290" target="_blank"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-pdf-download"></use></svg> <span class="share-link-text"> Download PDF </span> </a> </li> <li class="share-link share-link-print" data-component="print"> <a href="#" class="print"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-print"></use></svg> <span class="share-link-text"> Print </span> </a> </li> <li class="share-link share-link-discussion" data-component="share"> <a class="share-link-comments" href="#comments"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-comment"></use></svg> <span class="share-link-text">Join the Discussion</span> </a> </li> <li class="share-link share-link-dl"> <a href="https://dl.acm.org/doi/10.1145/3653290"> <svg aria-hidden="true" focusable="false" width="21" height="21" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-digital-library"></use></svg> <span class="share-link-text"> View in the ACM Digital Library </span> <svg aria-hidden="true" focusable="false" width="14" height="9" fill="var(--cacm--symbol--fill)" class="icon-dl"><use href="#am-symbol-icon-arrow-right"></use></svg> </a> </li> </ul> </div> </div> </header> <section class="article-table-of-contents" data-component="articleToc"> <ol class="article-table-of-contents__list"> <ul> <li><a href="#references">References</a></li> </ul> </ol> </section> <div class="article-contents"> <div class="article-content entry-content"> <article><div class="body" lang="en"><section id="sec1" class="sec"><p id="p-1">Our research group at the Instituto de Matemáticas of the Universidad Nacional Autónoma de México focuses in studying the principles underlying distributed computing, which covers a wide range of services in our everyday life, for example, cloud storage, cryptocurrencies, collaborative editing, as well as concurrent software that governs modern multicore computers. The goal of our discussion here is to survey our recent advances on one of our research lines: concurrent data structures. This type of data structures has attracted a great deal of interest as they are a key factor to exploit the inherent parallelism in modern multicore architectures, ubiquitous since the beginning of this century (see for example Herlihy<a class="reference-link xref xref-bibr" href="#B10" data-jats-ref-type="bibr" data-jats-rid="B10"><sup>10</sup></a> and Shavit<a class="reference-link xref xref-bibr" href="#B12" data-jats-ref-type="bibr" data-jats-rid="B12"><sup>12</sup></a>).</p><p id="p-2">In a concurrent implementation of a data structure, a pool of threads modify the contents of the structure at unpredictable times, since they run asynchronously, through the operations provided by the data structure. Furthermore, the operations of different threads might overlap in time, because the threads themselves need to implement the data structure using the underlying coordination primitives provided by the operating systems, such as read/write on shared registers, compare set, and others. See Figure <a class="xref xref-fig" href="#F1" data-jats-ref-type="fig" data-jats-rid="F1">1</a> for an example of an execution of a concurrent stack with three threads.</p><figure id="F1" class="fig" data-jats-position="float"><div class="image-container"> <a data-fslightbox="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig01.jpg" data-type="image" data-caption="Figure 1. A linearizable stack execution for three threads, T1, T2 and T3. Horizontal double-headed arrows denote the time that elapses between the invocation and response of a thread’s operation." href="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig01.jpg"> <img decoding="async" class="graphic" title="Figure 1. A linearizable stack execution for three threads, T1, T2 and T3. Horizontal double-headed arrows denote the time that elapses between the invocation and response of a thread’s operation." src="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig01.jpg" alt="A linearizable stack execution for three threads, T1, T2 and T3. Horizontal double-headed arrows denote the time that elapses between the invocation and response of a thread’s operation." data-image-id="F1" data-image-type="figure" /> </a> </div><figcaption><span class="caption-label">Figure 1. </span> <span class="title">A linearizable stack execution for three threads, <i>T</i>1, <i>T</i>2 and <i>T</i>3. Horizontal double-headed arrows denote the time that elapses between the invocation and response of a thread’s operation.</span><div class="figcaption-footer"> </div></figcaption></figure><p id="p-3">How do we know that a concurrent implementation of a stack is correct? What do we even mean by a “concurrent stack?” What do we mean by a “queue” if several threads can enqueue an item concurrently? In the classic case of sequential implementations there is a unique, “natural” definition of a data structure such as a queue or a stack. In contrast, in the concurrent world, this is not always the case, one can define correctness of concurrent implementations in several different ways, each of them useful in different applications.</p><p id="p-4">The gold standard of correctness condition for concurrent implementations is linearizability.<a class="reference-link xref xref-bibr" href="#B11" data-jats-ref-type="bibr" data-jats-rid="B11"><sup>11</sup></a> Linearizability states that every operation appears as if it takes effect “instantaneously” at a unique point in time between its invocation and response. These sequence of linearization points induce a sequential execution of the operations, and the execution is correct, or linearizable, if there are linearization points that induce a sequential execution that satisfies the sequential specification of the object implemented. Figure <a class="xref xref-fig" href="#F1" data-jats-ref-type="fig" data-jats-rid="F1">1</a> shows linearization points that induce a valid stack sequential execution.</p><p id="p-5">Linearizability is so popular because of its practical usefulness and its theoretical properties. From the practical side, for example, it allows the design of concurrent software in a modular manner, which is key for the design and implementation of large-scale systems. Namely, if one designs independently two linearizable objects, it is guaranteed a system that uses both is also linearizable.</p><p id="p-6">Despite all its benefits, after years of research, it is now well understood that linearizability has some inherent limitations. We provide two examples. There are concurrent data structures that cannot be analyzed through linearizability, since they do not have a sequential specification. For example, the exchanger object in the concurrent package of Java, which serves as a synchronization point where threads exchange items concurrently, has no sequential specification, because in sequential executions no exchanges take place. A second example is that it has been formally shown that some common data structures, such as sets, queues, stacks, and work-stealing for dynamic load balancing, only admit linearizable implementations that are inherently slow, for example Attiya et al.<a class="reference-link xref xref-bibr" href="#B1" data-jats-ref-type="bibr" data-jats-rid="B1"><sup>1</sup></a></p><p id="p-7">In the past few years, part of the research in our group has been devoted to developing techniques to overcome the limitations of linearizability. We proposed an extension of linearizability, called interval-linearizability, that is expressive enough to specify data structures that are impossible to specify with linearizability<a class="reference-link xref xref-bibr" href="#B5" data-jats-ref-type="bibr" data-jats-rid="B5"><sup>5</sup></a><sup>,</sup><a class="reference-link xref xref-bibr" href="#B6" data-jats-ref-type="bibr" data-jats-rid="B6"><sup>6</sup></a> (such as the exchanger object); hence one can, for the first time, formally reason about correctness for them. These types of structures are “truly” concurrent, which is forbidden in linearizable specifications and implementations.</p><p id="p-8">Generally, in an interval-linearizable implementation, every operation takes effect “continuously” in an interval of time, instead of instantaneously at a single point. During the interval, the operation might affect, or be affected by, the other operations whose linearization intervals it overlaps with, which is the mechanism that allows truly concurrent behaviors to be specified. Figure <a class="xref xref-fig" href="#F2" data-jats-ref-type="fig" data-jats-rid="F2">2</a> depicts an example of an execution of a counter with an interval-linearizable query operation. Thus, linearizability is nothing else than interval-linearizability when all intervals are just points.</p><figure id="F2" class="fig" data-jats-position="float"><div class="image-container"> <a data-fslightbox="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig02.jpg" data-type="image" data-caption="Figure 2. An interval-linearizable execution of a relaxed counter for three threads, T1, T2 and T3. Operation update, which adds a natural number to the current state of the counter, is linearizable, namely, it always takes effect at a single point. In contrast, operation query takes effect at an interval of time, returning a value that lies in the interval of integers defined by the state of the counter before and after the linearization interval of the operation." href="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig02.jpg"> <img decoding="async" class="graphic" title="Figure 2. An interval-linearizable execution of a relaxed counter for three threads, T1, T2 and T3. Operation update, which adds a natural number to the current state of the counter, is linearizable, namely, it always takes effect at a single point. In contrast, operation query takes effect at an interval of time, returning a value that lies in the interval of integers defined by the state of the counter before and after the linearization interval of the operation." src="https://cacm.acm.org/wp-content/uploads/2024/07/3653290_fig02.jpg" alt="An interval-linearizable execution of a relaxed counter for three threads, T1, T2 and T3. Operation update, which adds a natural number to the current state of the counter, is linearizable, namely, it always takes effect at a single point. In contrast, operation query takes effect at an interval of time, returning a value that lies in the interval of integers defined by the state of the counter before and after the linearization interval of the operation." data-image-id="F2" data-image-type="figure" /> </a> </div><figcaption><span class="caption-label">Figure 2. </span> <span class="title">An interval-linearizable execution of a relaxed counter for three threads, <i>T</i>1, <i>T</i>2 and <i>T</i>3. Operation update, which adds a natural number to the current state of the counter, is linearizable, namely, it always takes effect at a single point. In contrast, operation query takes effect at an interval of time, returning a value that lies in the interval of integers defined by the state of the counter before and after the linearization interval of the operation.</span><div class="figcaption-footer"> </div></figcaption></figure><p id="p-9">The interval-linearizability condition allowed us to formally specify new relaxed variants of classic data structures, such as queues and stacks and work-stealing, and provide simple and efficient implementations,<a class="reference-link xref xref-bibr" href="#B7" data-jats-ref-type="bibr" data-jats-rid="B7"><sup>7</sup></a> some of them delivering a good performance when combined with solutions to practical parallel problems.<a class="reference-link xref xref-bibr" href="#B4" data-jats-ref-type="bibr" data-jats-rid="B4"><sup>4</sup></a></p><p id="p-10">A challenging task by itself is that of proving linearizability of an implementation, due to the large number of possible executions implementations can exhibit (it has been formally shown that deciding if a finite execution is linearizable is NP-complete, for some concurrent objects<a class="reference-link xref xref-bibr" href="#B9" data-jats-ref-type="bibr" data-jats-rid="B9"><sup>9</sup></a>). The formal verification community has provided different techniques to tackle this problem, each of them providing different levels of guarantees. Despite all efforts, proving linearizability remains challenging. Our group has explored new static and dynamic techniques that help with this task. We have proposed new static techniques for modular formal verification of concurrent implementations,<a class="reference-link xref xref-bibr" href="#B3" data-jats-ref-type="bibr" data-jats-rid="B3"><sup>3</sup></a> as well as dynamic verification algorithmic approaches<a class="reference-link xref xref-bibr" href="#B2" data-jats-ref-type="bibr" data-jats-rid="B2"><sup>2</sup></a><sup>,</sup><a class="reference-link xref xref-bibr" href="#B8" data-jats-ref-type="bibr" data-jats-rid="B8"><sup>8</sup></a> that test at runtime whether the current execution of an implementation is linearizable, and possibly prevent side effects in case of non-linearizable executions.</p></section></div><footer class="back"></footer></article> </div> </div> <footer class="article-footer"> <section class="article-references" data-component="accordion" data-slide-to-refs="true"> <a name="references"></a> <button class="accordion-controller" aria-expanded="false"> <span class="article-references__title"> References </span> <span class="accordion-controller-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16" fill="var(--wp--preset--color--cacm-blue)"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </button> <ul class="article-references__text accordion-content"> <section id="references" class="ref-list-container"> <ul id="ref-list1" class="ref-list"> <li class="ref"> <div id="B1" class="citation"><span class="label">1.</span> <span class="mixed-citation" data-jats-publication-type="other"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Attiya</span>, <span class="given-names">H. </span></span><span class="etal">et al.</span> </span><span class="chapter-title">Laws of order: Expensive synchronization in concurrent algorithms cannot be eliminated</span>. In <span class="source"><em>Proceedings of the 38th ACM SIGPLAN-SIGACT Symp. Principles of Programming Languages</em></span>. <span class="person-group" data-jats-person-group-type="editor"><span class="string-name"><span class="surname">Ball, T.,</span></span> and <span class="string-name"><span class="surname">Sagiv</span></span>, M. (<span class="role">Eds.),</span> </span><span class="publisher-loc">Austin, TX, USA</span>, <span class="year">Jan. 26–28, 2011</span>, <span class="fpage">487</span>–<span class="lpage">498</span>.</span></div> </li> <li class="ref"> <div id="B2" class="citation"><span class="label">2.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Bonakdarpour</span>, <span class="given-names">B. </span></span><span class="etal">et al.</span> </span><span class="article-title">Decentralized asynchronous crash-resilient runtime verification</span>. <em><span class="source">J. ACM </span><span class="volume">69</span></em>, <span class="issue">5</span> (<span class="year">2022</span>), <span class="fpage">34:1</span>–<span class="lpage">34:31</span>.</span></div> </li> <li class="ref"> <div id="B3" class="citation"><span class="label">3.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span>, <span class="string-name"><span class="surname">Hurault</span>, <span class="given-names">A.</span></span>, <span class="string-name"><span class="surname">Quéinnec</span>, <span class="given-names">P.</span></span>, and <span class="string-name"><span class="surname">Roy</span>, <span class="given-names">M.</span></span> </span><span class="article-title">Tasks in modular proofs of concurrent algorithms</span>. <em><span class="source">Inf. Comput. </span><span class="volume">292</span></em>, (<span class="year">2023</span>), <span class="fpage">105040</span>.</span></div> </li> <li class="ref"> <div id="B4" class="citation"><span class="label">4.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span> and <span class="string-name"><span class="surname">Piña</span>, <span class="given-names">M.</span></span> </span><span class="article-title">Read/write fence-free work-stealing with multiplicity</span>. <em><span class="source">J. Parallel Distributed Comput. </span><span class="volume">186</span></em>, (<span class="year">2024</span>), <span class="fpage">104816</span>.</span></div> </li> <li class="ref"> <div id="B5" class="citation"><span class="label">5.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span>, <span class="string-name"><span class="surname">Rajsbaum</span>, <span class="given-names">S.</span></span>, and <span class="string-name"><span class="surname">Raynal</span>, <span class="given-names">M.</span></span> </span><span class="article-title">Unifying concurrent objects and distributed tasks: Interval-linearizability</span>. <em><span class="source">J. ACM </span><span class="volume">65</span></em>, <span class="issue">6</span> (<span class="year">2018</span>), <span class="fpage">45:1</span>–<span class="lpage">45:42</span>.</span></div> </li> <li class="ref"> <div id="B6" class="citation"><span class="label">6.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span>, <span class="string-name"><span class="surname">Rajsbaum</span>, <span class="given-names">S.</span></span>, and <span class="string-name"><span class="surname">Raynal</span>, <span class="given-names">M.</span></span> </span><span class="article-title">A linearizability-based hierarchy for concurrent specifications</span>. <em><span class="source">Commun. ACM </span><span class="volume">66</span></em>, <span class="issue">1</span> (<span class="year">Jan. 2023</span>), <span class="fpage">86</span>–<span class="lpage">97</span>.</span></div> </li> <li class="ref"> <div id="B7" class="citation"><span class="label">7.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span>, <span class="string-name"><span class="surname">Rajsbaum</span>, <span class="given-names">S.</span></span>, and <span class="string-name"><span class="surname">Raynal</span>, <span class="given-names">M.</span></span> </span><span class="article-title">Set-linearizable implementations from read/write operations: Sets, fetch & increment, stacks and queues with multiplicity</span>. <em><span class="source">Distributed Comput. </span><span class="volume">36</span></em>, <span class="issue">2</span> (<span class="year">2023</span>), <span class="fpage">89</span>–<span class="lpage">106</span>.</span></div> </li> <li class="ref"> <div id="B8" class="citation"><span class="label">8.</span> <span class="mixed-citation" data-jats-publication-type="other"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Castañeda</span>, <span class="given-names">A.</span></span> and <span class="string-name"><span class="surname">Rodríguez</span>, <span class="given-names">G.V.</span></span> </span><span class="article-title">Asynchronous wait-free runtime verification and enforcement of linearizability</span>. In <span class="source"><em>Proceedings of the 2023 ACM Symp. Principles of Distributed Computing</em> </span>(<span class="year">2023</span>), <span class="fpage">90</span>–<span class="lpage">101</span>.</span></div> </li> <li class="ref"> <div id="B9" class="citation"><span class="label">9.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Gibbons</span>, <span class="given-names">P.B.</span></span> and <span class="string-name"><span class="surname">Korach</span>, <span class="given-names">E.</span></span> </span><span class="article-title">Testing shared memories</span>. <em><span class="source">SIAM J. Comput. </span><span class="volume">26</span></em>, <span class="issue">4</span> (<span class="year">1997</span>), <span class="fpage">1208</span>–<span class="lpage">1244</span>.</span></div> </li> <li class="ref"> <div id="B10" class="citation"><span class="label">10.</span> <span class="mixed-citation" data-jats-publication-type="book"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Herlihy</span>, <span class="given-names">M.</span></span> and <span class="string-name"><span class="surname">Shavit</span>, <span class="given-names">N.</span></span> </span><span class="source">The Art of Multiprocessor Programming</span>. <span class="publisher-name">Morgan Kaufmann</span>, <span class="year">2008</span>.</span></div> </li> <li class="ref"> <div id="B11" class="citation"><span class="label">11.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Herlihy</span>, <span class="given-names">M.</span></span> and <span class="string-name"><span class="surname">Wing</span>, <span class="given-names">J.M.</span></span> </span><span class="article-title">Linearizability: A correctness condition for concurrent objects</span>. <em><span class="source">ACM Trans. Program. Lang. Syst. </span><span class="volume">12</span></em>, <span class="issue">3</span> (<span class="year">1990</span>), <span class="fpage">463</span>–<span class="lpage">492</span>.</span></div> </li> <li class="ref"> <div id="B12" class="citation"><span class="label">12.</span> <span class="mixed-citation" data-jats-publication-type="journal"><span class="person-group" data-jats-person-group-type="author"><span class="string-name"><span class="surname">Shavit</span>, <span class="given-names">N.</span></span> </span><span class="article-title">Data structures in the multicore age</span>. <em><span class="source">Commun. ACM </span><span class="volume">54</span></em>, <span class="issue">3</span> (<span class="year">Mar. 2011</span>), <span class="fpage">76</span>–<span class="lpage">84</span>.</span></div> </li> </ul> </section> </ul> </section> <section id="authors" class="article-authors" data-component="accordion"> <button class="accordion-controller" aria-expanded="false"> <span class="article-authors__title"> About the Authors </span> <span class="accordion-controller-icon"> <svg aria-hidden="true" focusable="false" width="16" height="16" fill="var(--wp--preset--color--cacm-blue)"><use href="#am-symbol-icon-chevron-down"></use></svg> </span> </button> <div class="article-authors__info accordion-content"> <div class="article-authors__info-text"> <section id="sec2" class="biography"> <p id="p-1"><b>Armando Castañeda</b>, Instituto de Matemáticas, UNAM, Mexico.</p> <p id="p-2"><b>Sergio Rajsbaum</b>, Instituto de Matemáticas, UNAM, Mexico, visiting IRIF-Université Paris Cité.</p> </section> </div> </div> </section> <ul class="share"> <li class="share-link" data-component="share"> <a href="#" class="share-toggle"> <svg aria-hidden="true" focusable="false" width="19" height="18" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-share"></use></svg> <span class="share-link-text"> Share </span> </a> <ul class="share-menu" aria-hidden="true"> <li> <a href="https://twitter.com/intent/tweet?url=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&text=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Twitter </a> </li> <li> <a href="http://www.reddit.com/submit?url=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&title=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Reddit </a> </li> <li> <a href="https://news.ycombinator.com/submitlink?u=https://cacm.acm.org/latin-america-regional-special-section/recent-advances-on-principles-of-concurrent-data-structures/&t=Recent%20Advances%20on%20Principles%20of%20Concurrent%20Data%20Structures" target="_blank"> Hacker News </a> </li> </ul> </li> <li class="share-link share-link-pdf"> <a href="https://dl.acm.org/doi/pdf/10.1145/3653290" target="_blank"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-pdf-download"></use></svg> <span class="share-link-text"> Download PDF </span> </a> </li> <li class="share-link share-link-print" data-component="print"> <a href="#" class="print"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-print"></use></svg> <span class="share-link-text"> Print </span> </a> </li> <li class="share-link share-link-discussion" data-component="share"> <a class="share-link-comments" href="#comments"> <svg aria-hidden="true" focusable="false" width="19" height="20" fill="var(--cacm--symbol--fill)"><use href="#am-symbol-icon-comment"></use></svg> <span class="share-link-text">Join the Discussion</span> </a> </li> </ul> </footer> <div class="article-authors-digital-library"> <section class="article-submission"> <div class="article-submission__cta"> <div class="article-submission__cta-container"> <p class="article-submission__cta-title"> Submit an Article to CACM </p> <p class="article-submission__cta-text"> CACM welcomes unsolicited <a href="https://cacm.acm.org/author-guidelines/#CACMsubmission">submissions</a> on topics of relevance and value to the computing community. </p> </div> </div> </section> <section class="article-digital-library"> <div class="article-digital-library__article-info"> <p class="article-digital-library__intro-text"> You Just Read </p> <h4 class="article-digital-library__title"> Recent Advances on Principles of Concurrent Data Structures </h4> <a class="article-digital-library__link" href="https://dl.acm.org/doi/10.1145/3653290"> <svg aria-hidden="true" focusable="false" width="21" height="21" fill="var(--wp--preset--color--cacm-black)"><use href="#am-symbol-icon-digital-library"></use></svg> View in the ACM Digital Library <svg aria-hidden="true" focusable="false" width="14" height="9" fill="var(--wp--preset--color--cacm-black)" class="icon-dl"><use href="#am-symbol-icon-arrow-right"></use></svg> </a> </div> <div class="article-digital-library__copyright-info"> <p>© 2024 Copyright held by the owner/author(s). Publication rights licensed to ACM.</p> </div> </section> </div> <div class="article-sidebar"> <section class="article-doi"> <h3 class="article-doi__heading">DOI</h3> 10.1145/3653290</section> <section class="article-issue"> <div class="article-issue__meta"> <h3 class="article-issue__heading">August 2024 Issue</h3> <p class="article-issue__vol-info">Vol. 67 No. 8</p> <p class="article-issue__page-info">Pages: 45-46</p> </div> <a href="https://cacm.acm.org/issue/august-2024/" class="article-issue__toc-link"> Table of Contents <span class="article-issue__toc-icon-arrow"><svg aria-hidden="true" focusable="false" width="14" height="9" fill="var(--wp--preset--color--cacm-blue)"><use href="#am-symbol-icon-arrow-right"></use></svg></span> </a> </section> <section class="article-related"> <div class="article-related-content"> <h3 class="article-related__heading">Related Reading</h3>  <ul> <li class="article-related-item"> <p class="article-related-section"> <a href="https://cacm.acm.org/section/opinion/">Opinion</a> </p> <p class="article-related-title"> <a href="https://cacm.acm.org/opinion/the-data-structure-canon/"> The Data-Structure Canon </a> </p> <p class="article-related-topic"> <a href="https://cacm.acm.org/category/computing-applications/">Computing Applications</a> </p> </li> <li class="article-related-item"> <p class="article-related-section"> <a href="https://cacm.acm.org/section/research/">Research and Advances</a> </p> <p class="article-related-title"> <a href="https://cacm.acm.org/research/data-structures-in-the-multicore-age/"> Data Structures in the Multicore Age </a> </p> <p class="article-related-topic"> <a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/">Artificial Intelligence and Machine Learning</a> </p> </li> <li class="article-related-item"> <p class="article-related-section"> <a href="https://cacm.acm.org/section/research/">Research and Advances</a> </p> <p class="article-related-title"> <a href="https://cacm.acm.org/research/structured-data-structures/"> Structured data structures </a> </p> <p class="article-related-topic"> <a href="https://cacm.acm.org/category/computing-applications/">Computing Applications</a> </p> </li> <li class="article-related-item"> <p class="article-related-section"> <a href="https://cacm.acm.org/section/practice/">Practice</a> </p> <p class="article-related-title"> <a href="https://cacm.acm.org/practice/proving-the-correctness-of-nonblocking-data-structures/"> Proving the Correctness of Nonblocking Data Structures </a> </p> <p class="article-related-topic"> <a href="https://cacm.acm.org/category/computing-applications/">Computing Applications</a> </p> </li> </ul> </div> </section> <div class="ad ad-mobile ad--is-loading" data-component="ad" data-platform="mobile" data-show-ad="false"> <div class="cacm-ad-unit"> <p class="ad-label">Advertisement</p> <div class="ad-unit" data-pipeline-id="684700" data-dimension-id="599027"></div> <noscript><a href="https://acm.nui.media/pipeline/684700/0/cc?z=acm"><img src="https://acm.nui.media/pipeline/684700/0/vc?z=acm&dim=599027&kw=&click=&abr=$imginiframe" alt="" ></a></noscript> </div> </div> <div class="ad ad-desktop ad--is-loading" data-component="ad" data-platform="desktop" data-show-ad="false"> <div class="cacm-ad-unit"> <p class="ad-label">Advertisement</p> <div class="ad-unit" data-pipeline-id="684700" data-dimension-id="599027"></div> <noscript><a href="https://acm.nui.media/pipeline/684700/0/cc?z=acm"><img src="https://acm.nui.media/pipeline/684700/0/vc?z=acm&dim=599027&kw=&click=&abr=$imginiframe" alt="" ></a></noscript> </div> </div> </div> <section class="article-comments"> <div class="article-comments__inner container"> <h3 class="article-comments__heading"> Join the Discussion (0) </h3> <section class="cta-join-the-discussion" id="article-discussion"> <div class="cta-join-the-discussion__box"> <h4 class="cta-join-the-discussion__heading">Become a Member or Sign In to Post a Comment</h4> <div class="cta-join-the-discussion__button-group"> <a class="cta-join-the-discussion__button cta-join-the-discussion__button--login" href="https://cacm.acm.org/wp-login.php?saml_sso">Sign In</a> <a class="cta-join-the-discussion__button cta-join-the-discussion__button--signup" href="https://accounts.acm.org/">Sign Up</a> </div> </div> </section> <div id="comments" class="comments-area"> <div id="respond" class="auth-comment-form" data-component="authCommentForm" data-replytocom="0"> <div class="auth-comment-form__contents"> <span class="auth-comment-form__loader"> <svg version="1.1" id="L9" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 100 100" enable-background="new 0 0 0 0" xml:space="preserve"> <path fill="var(--wp--preset--color--cacm-blue)" d="M73,50c0-12.7-10.3-23-23-23S27,37.3,27,50 M30.9,50c0-10.5,8.5-19.1,19.1-19.1S69.1,39.5,69.1,50"> <animateTransform attributeName="transform" attributeType="XML" type="rotate" dur="1s" from="0 50 50" to="360 50 50" repeatCount="indefinite" /> </path> </svg> </span> </div> </div> </div> </div> </section> <section class="post-list the-latest" data-layout="grid-three-up" data-component="postList" > <header class="section-header "> <h3 class="section-header__heading" > <a class="section-header__heading-link" href="/?s="> The Latest from CACM </a> </h3> <div class="section-header__readmore"> <a class="section-header__readmore-link" href="/?s=" aria-label=" Explore more from The Latest from CACM "> <span class="section-header__readmore-text">Explore More</span> <span class="section-header__readmore-icon"><svg aria-hidden="true" focusable="false" width="14" height="9"><use href="#am-symbol-icon-arrow-right"></use></svg></span> </a> </div> </header> <div class=""> <div class="post-list__content"><div class="post-list__item"> <article id="post-762633" class="post-list__post post-762633 post type-post status-publish format-standard has-post-thumbnail hentry category-artificial-intelligence-machine-learning category-security-and-privacy section-news"> <div class="post-list__post-content"> <div class="post-list__post-text"> <div class="post-list__post-eyebrow"> <a href="https://cacm.acm.org/section/news/">News</a> <span class="post-list__post-timestamp"><span class="posted-on"> Nov 21 2024</span></span> </div> <p class="post-list__post-heading"> <a href="https://cacm.acm.org/news/detecting-explaining-industrial-hacks/">Detecting/Explaining Industrial Hacks</a> </p> <div class="post-list__post-meta-group"> <div class="post-list__post-byline"> <a href="https://cacm.acm.org/author/r-colin-johnson/" title="Posts by R. Colin Johnson" class="author url fn" rel="author">R. Colin Johnson</a> </div> <span class="post-list__post-topic"><a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/">Artificial Intelligence and Machine Learning</a></span> </div> </div> <figure class="post-list__post-figure"> <a href="https://cacm.acm.org/news/detecting-explaining-industrial-hacks/" aria-label="Detecting/Explaining Industrial Hacks" aria-hidden="true" tabindex="-1"> <div class="image-wrapper image-wrapper--widescreen"><img width="1024" height="576" src="https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg" class="attachment-full size-full" alt="crack with light effect, illustration" decoding="async" srcset="https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg 2400w, https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg?resize=300,169 300w, https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg?resize=768,432 768w, https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg?resize=1024,576 1024w, https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg?resize=1536,864 1536w, https://cacm.acm.org/wp-content/uploads/2024/11/112024.News_.Detecting-Explaining-S.jpg?resize=2048,1152 2048w" sizes="(max-width: 1024px) 100vw, 1024px" /></div> </a> </figure> </div> </article> </div> <div class="post-list__item"> <article id="post-762600" class="post-list__post post-762600 post type-post status-publish format-standard has-post-thumbnail hentry category-artificial-intelligence-machine-learning category-security-and-privacy section-news"> <div class="post-list__post-content"> <div class="post-list__post-text"> <div class="post-list__post-eyebrow"> <a href="https://cacm.acm.org/section/news/">News</a> <span class="post-list__post-timestamp"><span class="posted-on"> Nov 20 2024</span></span> </div> <p class="post-list__post-heading"> <a href="https://cacm.acm.org/news/security-via-ai/">Security via AI</a> </p> <div class="post-list__post-meta-group"> <div class="post-list__post-byline"> <a href="https://cacm.acm.org/author/mark-halper/" title="Posts by Mark Halper" class="author url fn" rel="author">Mark Halper</a> </div> <span class="post-list__post-topic"><a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/">Artificial Intelligence and Machine Learning</a></span> </div> </div> <figure class="post-list__post-figure"> <a href="https://cacm.acm.org/news/security-via-ai/" aria-label="Security via AI" aria-hidden="true" tabindex="-1"> <div class="image-wrapper image-wrapper--widescreen"><img width="1024" height="577" src="https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg" class="attachment-full size-full" alt="two figures competing, illustration" decoding="async" srcset="https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg 2400w, https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg?resize=300,169 300w, https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg?resize=768,433 768w, https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg?resize=1024,577 1024w, https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg?resize=1536,865 1536w, https://cacm.acm.org/wp-content/uploads/2024/11/111524.News_.Security-via-AI-G.jpg?resize=2048,1154 2048w" sizes="(max-width: 1024px) 100vw, 1024px" /></div> </a> </figure> </div> </article> </div> <div class="post-list__item"> <article id="post-762498" class="post-list__post post-762498 post type-post status-publish format-standard has-post-thumbnail hentry category-artificial-intelligence-machine-learning category-data-and-information section-news"> <div class="post-list__post-content"> <div class="post-list__post-text"> <div class="post-list__post-eyebrow"> <a href="https://cacm.acm.org/section/news/">News</a> <span class="post-list__post-timestamp"><span class="posted-on"> Nov 14 2024</span></span> </div> <p class="post-list__post-heading"> <a href="https://cacm.acm.org/news/the-ai-spy/">The AI Spy</a> </p> <div class="post-list__post-meta-group"> <div class="post-list__post-byline"> <a href="https://cacm.acm.org/author/karen-emslie/" title="Posts by Karen Emslie" class="author url fn" rel="author">Karen Emslie</a> </div> <span class="post-list__post-topic"><a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/">Artificial Intelligence and Machine Learning</a></span> </div> </div> <figure class="post-list__post-figure"> <a href="https://cacm.acm.org/news/the-ai-spy/" aria-label="The AI Spy" aria-hidden="true" tabindex="-1"> <div class="image-wrapper image-wrapper--widescreen"><img width="1024" height="576" src="https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg" class="attachment-full size-full" alt="digital keyhole, illustration" decoding="async" srcset="https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg 2277w, https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg?resize=300,169 300w, https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg?resize=768,432 768w, https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg?resize=1024,576 1024w, https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg?resize=1536,864 1536w, https://cacm.acm.org/wp-content/uploads/2024/11/111424.News_.The-AI-Spy-G.jpg?resize=2048,1152 2048w" sizes="(max-width: 1024px) 100vw, 1024px" /></div> </a> </figure> </div> </article> </div> </div> </div> </section> <div class="cta-membership cta-membership--no-js" data-component="ctaMembership"> <section class="cta-become-a-member"> <div class="cta-become-a-member__inner container"> <h3 class="cta-become-a-member__heading"> Shape the Future of Computing </h3> <p class="cta-become-a-member__description"> ACM encourages its members to take a direct hand in shaping the future of the association. There are more ways than ever to get involved. </p> <a class="cta-become-a-member__link" href="https://www.acm.org/about-acm/get-involved"> Get Involved </a> </div> </section> <section class="cta-open-access"> <div class="cta-open-access__inner container"> <h3 class="cta-open-access__heading"> Communications of the ACM (CACM) is now a fully Open Access publication. </h3> <p class="cta-open-access__description"> By opening CACM to the world, we hope to increase engagement among the broader computer science community and encourage non-members to discover the rich resources ACM has to offer. </p> <a class="cta-open-access__link" href="https://cacm.acm.org/news/cacm-is-becoming-open-access"> Learn More </a> </div> </section> </div> </article> </main> </div> </div> <footer id="colophon" class="site-footer"> <div class="site-footer__inner container"> <div class="site-footer__columns"> <div class="site-footer__column site-footer__column-branding"> <a class="site-footer__logo" aria-label="Home" href="https://cacm.acm.org"> <svg aria-hidden="true" focusable="false" width="548" height="88" fill="#FFF"><use href="#am-symbol-cacm-logo"></use></svg> </a> <nav class="social-navigation"> <ul class="social-navigation__list"> <li> <a href="https://twitter.com/cacmmag"> <span class="screen-reader-only">CACM on Twitter</span> <svg aria-hidden="true" focusable="false" width="38" height="38" fill="#fff"><use href="#am-symbol-icon-social-twitter"></use></svg> </a> </li> <li> <a href="https://www.reddit.com/user/TheOfficialACM"> <span class="screen-reader-only">CACM on Reddit</span> <svg aria-hidden="true" focusable="false" width="38" height="38" fill="#fff"><use href="#am-symbol-icon-social-reddit"></use></svg> </a> </li> <li> <a href="https://www.linkedin.com/groups/36836/"> <span class="screen-reader-only">CACM on LinkedIn</span> <svg aria-hidden="true" focusable="false" width="38" height="38" fill="#fff"><use href="#am-symbol-icon-social-linkedin"></use></svg> </a> </li> </ul> </nav> </div> <div class="site-footer__column site-footer__column-topics"> <div class="site-footer__topics-menu"> <p class="site-footer__heading"> Topics </p> <ul class="site-footer__topics-menu__list"> <li> <a href="https://cacm.acm.org/category/architecture-and-hardware/"> Architecture and Hardware </a> </li> <li> <a href="https://cacm.acm.org/category/artificial-intelligence-machine-learning/"> Artificial Intelligence and Machine Learning </a> </li> <li> <a href="https://cacm.acm.org/category/computer-history/"> Computer History </a> </li> <li> <a href="https://cacm.acm.org/category/computing-applications/"> Computing Applications </a> </li> <li> <a href="https://cacm.acm.org/category/computing-profession/"> Computing Profession </a> </li> <li> <a href="https://cacm.acm.org/category/data-and-information/"> Data and Information </a> </li> <li> <a href="https://cacm.acm.org/category/education/"> Education </a> </li> <li> <a href="https://cacm.acm.org/category/hci/"> HCI </a> </li> <li> <a href="https://cacm.acm.org/category/philosophy-of-computing/"> Philosophy of Computing </a> </li> <li> <a href="https://cacm.acm.org/category/security-and-privacy/"> Security and Privacy </a> </li> <li> <a href="https://cacm.acm.org/category/society/"> Society </a> </li> <li> <a href="https://cacm.acm.org/category/software-engineering-and-programming-languages/"> Software Engineering and Programming Languages </a> </li> <li> <a href="https://cacm.acm.org/category/systems-and-networking/"> Systems and Networking </a> </li> <li> <a href="https://cacm.acm.org/category/theory/"> Theory </a> </li> </ul> </div> </div> <div class="site-footer__column site-footer__column-about"> <div class="site-footer__menu-magazine"> <p class="site-footer__heading">Magazine</p> <ul id="menu-magazine-footer" class="site-footer__menu-magazine-menu"><li class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217988"><a href="/issue/latest/" id="menu-link-10">Latest Issue</a></li> <li class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217989"><a href="/issues/" id="menu-link-11">Magazine Archive</a></li> <li class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224644"><a href="https://cacm.acm.org/editorial-staff-board/" id="menu-link-12">Editorial Staff and Board</a></li> <li class="menu-item menu-item-type-custom menu-item-object-custom menu-item-751386"><a href="https://cacm.acm.org/author-guidelines#CACMsubmission" id="menu-link-13">Submit an Article</a></li> <li class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224585"><a href="https://cacm.acm.org/feeds-2/" id="menu-link-14">Alerts & Feeds</a></li> <li class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224645"><a href="https://cacm.acm.org/author-guidelines/" id="menu-link-15">Author Guidelines</a></li> </ul> </div> <div class="site-footer__menu-communications"> <p class="site-footer__heading">Communications of the ACM</p> <ul id="menu-communications-footer" class="site-footer-communications-menu"><li id="menu-item-224637" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224637"><a href="https://cacm.acm.org/about-us/" id="menu-link-16">About Us</a></li> <li id="menu-item-224664" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224664"><a href="https://cacm.acm.org/faq/" id="menu-link-17">Frequently Asked Questions</a></li> <li id="menu-item-224638" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224638"><a href="https://cacm.acm.org/contact-us/" id="menu-link-18">Contact Us</a></li> <li id="menu-item-217972" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217972"><a href="https://www.acm.org/publications/advertising" id="menu-link-19">For Advertisers</a></li> <li id="menu-item-224639" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-224639"><a href="https://cacm.acm.org/join-acm/" id="menu-link-20">Join ACM</a></li> </ul> </div> </div> </div> <div class="site-footer__info"> <div class="site-footer__info__inner"> <p class="site-footer__info-copyright"><small> © 2024 Communications of the ACM. All Rights Reserved. </small></p> <div class="menu-policy-menu-container"><ul id="menu-policy-footer" class="site-footer__info-policy-list"><li id="menu-item-217993" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217993"><a href="https://www.acm.org/cookie-notice" id="menu-link-21">Cookie Notice</a></li> <li id="menu-item-217994" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-217994"><a href="https://www.acm.org/about-acm/privacy-policy" id="menu-link-22">Privacy Policy</a></li> </ul></div> </div> </div> </div> </footer> </div> <script type="text/javascript" src="https://cacm.acm.org/wp-content/themes/cacm/client/build/js/global.bundle.min.js?ver=e97a984b44ccc756957f" id="cacm-global-js"></script> <script type="text/javascript" src="https://cacm.acm.org/wp-includes/js/dist/hooks.min.js?ver=4d63a3d491d11ffd8ac6" id="wp-hooks-js"></script> <script type="text/javascript" src="https://cacm.acm.org/wp-includes/js/dist/i18n.min.js?ver=5e580eb46a90c2b997e6" id="wp-i18n-js"></script> <script type="text/javascript" id="wp-i18n-js-after"> /* <![CDATA[ */ wp.i18n.setLocaleData( { 'text direction\u0004ltr': [ 'ltr' ] } ); /* ]]> */ </script> <script type="text/javascript" id="cacm-article-js-extra"> /* <![CDATA[ */ var cacmLocalVars = {"restCommentsUrl":"https:\/\/cacm.acm.org\/wp-json\/wp\/v2\/comments","restCommentFormUrl":"https:\/\/cacm.acm.org\/wp-json\/cacm-plugin\/v1\/comment\/form\/758290"}; /* ]]> */ </script> <script type="text/javascript" src="https://cacm.acm.org/wp-content/themes/cacm/client/build/js/article.bundle.min.js?ver=237e66042b6c917cfd09" id="cacm-article-js"></script> <script type="text/javascript" src="https://cacm.acm.org/wp-includes/js/comment-reply.min.js?ver=6.7.1" id="comment-reply-js" async="async" data-wp-strategy="async"></script> <script type="text/javascript" src="https://stats.wp.com/e-202447.js" id="jetpack-stats-js" data-wp-strategy="defer"></script> <script type="text/javascript" id="jetpack-stats-js-after"> /* <![CDATA[ */ _stq = window._stq || []; _stq.push([ "view", JSON.parse("{\"v\":\"ext\",\"blog\":\"212686646\",\"post\":\"758290\",\"tz\":\"-5\",\"srv\":\"cacm.acm.org\",\"hp\":\"vip\",\"j\":\"1:13.9.1\"}") ]); _stq.push([ "clickTrackerInit", "212686646", "758290" ]); /* ]]> */ </script> <script type="text/javascript">(function(){var id="Sh2m7XRvbVWoA8uJG6g2wIBNDLfpsOxFx1ciwKwo";var js=document.createElement("script");js.setAttribute("type","text/javascript");js.setAttribute("src","//deploy.mopinion.com/js/pastease.js");js.async=true;document.getElementsByTagName("head")[0].appendChild(js);var t=setInterval(function(){try{Pastease.load(id);clearInterval(t)}catch(e){}},50)})();</script>  </body> </html>