75 lines
4.8 KiB
HTML
75 lines
4.8 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Title" content="Comparison of Just-In-Time compiler and direct processing" />
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<meta name="abstract" content="If you are trying to decide whether to use the Just-In-Time compiler or direct processing mode to run your Java program, this table provides additional information to help you make the best choice for your situation." />
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<meta name="description" content="If you are trying to decide whether to use the Just-In-Time compiler or direct processing mode to run your Java program, this table provides additional information to help you make the best choice for your situation." />
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<meta name="DC.Relation" scheme="URI" content="jit.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="jitde" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Comparison of Just-In-Time compiler and direct processing</title>
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</head>
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<body id="jitde"><a name="jitde"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Comparison of Just-In-Time compiler and direct processing</h1>
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<div><p>If you are trying to decide whether to use the Just-In-Time compiler
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or direct processing mode to run your Java™ program, this table provides additional
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information to help you make the best choice for your situation.</p>
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<p><a href="selmod.htm">Just-In-Time compiler or direct processing mode</a></p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e24">Just-In-Time compiler</th>
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<th valign="top" id="d0e26">Direct processing</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e24 ">Provides an automatic compilation of any method when needed. The JIT
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compiler can compile a method much faster than direct processing.</td>
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<td valign="top" headers="d0e26 ">Allows you to compile an entire class or JAR file by using the Create Java Program
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(CRTJVAPGM) control language (CL) command. If you do not compile the files,
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direct processing compiles the files automatically at run time.</td>
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</tr>
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<tr><td valign="top" headers="d0e24 ">Enables you to avoid using the CRTJVAPGM CL command during program
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development. You can also use the JIT compiler with highly dynamic
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applications that generate or discover code at run time.</td>
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<td valign="top" headers="d0e26 ">Most ready-to-deploy server applications use direct processing at optimization
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level 40 because they are likely to be in use by multiple users at any given
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time. Multiple user jobs share the same code space in memory, which reduces
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the memory footprint.</td>
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</tr>
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<tr><td valign="top" headers="d0e24 ">Rapidly performs complex optimizations and Java specific optimizations at run time.</td>
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<td valign="top" headers="d0e26 ">Enables complex optimizations, because direct processing does not perform
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optimization at run time. However, direct processing cannot always perform
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Java-specific optimizations (like inlining methods) because Java program
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objects must be independent.</td>
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</tr>
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<tr><td valign="top" headers="d0e24 ">Offers better code performance when compared to direct processing.
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In most cases, the performance of JIT-generated code is better than direct
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processing optimization level 40.</td>
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<td valign="top" headers="d0e26 ">Offers the only way your Java program can adopt owner authority.</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="jit.htm" title="A Just-In-Time (JIT) compiler is a platform-specific compiler that generates machine instructions for each method as needed.">Just-In-Time compiler</a></div>
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</div>
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</div>
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</body>
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</html>
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