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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>1.5 Implementations</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">The Racket Reference</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="model.html" class="tocviewselflink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Operations</a></td></tr><tr><td align="right">18 </td><td><a href="running.html" class="to
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its implementation. Nevertheless, some details inevitably vary with
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the implementation. Racket currently has two main implementations:</p><ul><li><p>The <a name="(tech._c)"></a><span style="font-style: italic">CS</span> implementation is the default implementation
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as of Racket version 8.0. This variant is called “CS” because
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it uses Chez Scheme as its core compiler and runtime system.</p><p>The CS implementation typically provides the best performance
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for Racket programs. Compiled Racket CS code in a
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<span class="stt">".zo"</span> file normally contains machine code that is
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specific to an operating system and architecture.</p></li><li><p>The <a name="(tech._bc)"></a><span style="font-style: italic">BC</span> implementation was the default implementation
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up until version 7.9. The “BC” label stands for “before
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Chez” or “bytecode.”</p><p>Compiled Racket BC code in a <span class="stt">".zo"</span> file normally
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contains platform-independent bytecode that is further compiled
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to machine code “just in time” as the code is loaded.</p><p>Racket BC has two variants: <a name="(tech._3m)"></a><span style="font-style: italic">3m</span> and <a name="(tech._cgc)"></a><span style="font-style: italic">CGC</span>.
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The difference is the <a href="eval-model.html#%28tech._garbage._collection%29" class="techoutside" data-pltdoc="x"><span class="techinside">garbage collection</span></a> implementation,
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where 3m uses a garbage collector that moves objects in memory
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(an effect that is visible to foreign libraries, for example)
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and keeps precise track of allocated objects, while CGC uses a
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“conservative” collector that requires less cooperation from
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an embedding foreign environment. The 3m subvariant tends to
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perform much better than CGC, and it became the default
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variant in version 370 (which would be v3.7 in the current
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versioning convention).</p></li></ul><p>Most Racket programs run the same in all implementation variants, but some Racket
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features are available only on some implementation variants, and the
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interaction of Racket and foreign functions is significantly different
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across the variants. Use <span class="RktSym"><a href="runtime.html#%28def._%28%28quote._~23~25kernel%29._system-type%29%29" class="RktValLink" data-pltdoc="x">system-type</a></span> to get information about
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the current running implementation.</p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" id="searchbox" type="text" tabindex="1" placeholder="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "8.6", "../");"/></form> <a href="https://docs.racket-lang.org/index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("8.6");">top</a><span class="tocsettoggle"> <a href="javascript:void(0);" title="show/hide table of contents" onclick="TocsetToggle();">contents</a></span></span><span class="navright"> <a href="printing.html" title="backward to "1.4 The Printer"" data-pltdoc="x">← prev</a> <a href="model.html" title="up to "1 Language Model"" data-pltdoc="x">up</a> <a href="notation.html" title="forward to "2 Notation for Documentation"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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