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183 lines
8.4 KiB
HTML
183 lines
8.4 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Profiling (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Profiling (GNU MP 6.1.0)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="GMP-Basics.html#GMP-Basics" rel="up" title="GMP Basics">
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<link href="Autoconf.html#Autoconf" rel="next" title="Autoconf">
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<link href="Debugging.html#Debugging" rel="prev" title="Debugging">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Profiling"></a>
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<div class="header">
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<p>
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Next: <a href="Autoconf.html#Autoconf" accesskey="n" rel="next">Autoconf</a>, Previous: <a href="Debugging.html#Debugging" accesskey="p" rel="prev">Debugging</a>, Up: <a href="GMP-Basics.html#GMP-Basics" accesskey="u" rel="up">GMP Basics</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Profiling-1"></a>
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<h3 class="section">3.13 Profiling</h3>
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<a name="index-Profiling"></a>
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<a name="index-Execution-profiling-1"></a>
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<a name="index-_002d_002denable_002dprofiling-1"></a>
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<p>Running a program under a profiler is a good way to find where it’s spending
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most time and where improvements can be best sought. The profiling choices
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for a GMP build are as follows.
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</p>
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<dl compact="compact">
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<dt>‘<samp>--disable-profiling</samp>’</dt>
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<dd><p>The default is to add nothing special for profiling.
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</p>
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<p>It should be possible to just compile the mainline of a program with <code>-p</code>
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and use <code>prof</code> to get a profile consisting of timer-based sampling of
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the program counter. Most of the GMP assembly code has the necessary symbol
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information.
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</p>
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<p>This approach has the advantage of minimizing interference with normal program
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operation, but on most systems the resolution of the sampling is quite low (10
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milliseconds for instance), requiring long runs to get accurate information.
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</p>
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</dd>
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<dt>‘<samp>--enable-profiling=prof</samp>’</dt>
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<dd><a name="index-prof"></a>
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<p>Build with support for the system <code>prof</code>, which means ‘<samp>-p</samp>’ added
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to the ‘<samp>CFLAGS</samp>’.
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</p>
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<p>This provides call counting in addition to program counter sampling, which
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allows the most frequently called routines to be identified, and an average
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time spent in each routine to be determined.
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</p>
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<p>The x86 assembly code has support for this option, but on other processors
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the assembly routines will be as if compiled without ‘<samp>-p</samp>’ and therefore
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won’t appear in the call counts.
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</p>
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<p>On some systems, such as GNU/Linux, ‘<samp>-p</samp>’ in fact means ‘<samp>-pg</samp>’ and in
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this case ‘<samp>--enable-profiling=gprof</samp>’ described below should be used
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instead.
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</p>
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</dd>
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<dt>‘<samp>--enable-profiling=gprof</samp>’</dt>
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<dd><a name="index-gprof"></a>
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<p>Build with support for <code>gprof</code>, which means ‘<samp>-pg</samp>’ added to the
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‘<samp>CFLAGS</samp>’.
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</p>
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<p>This provides call graph construction in addition to call counting and program
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counter sampling, which makes it possible to count calls coming from different
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locations. For example the number of calls to <code>mpn_mul</code> from
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<code>mpz_mul</code> versus the number from <code>mpf_mul</code>. The program counter
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sampling is still flat though, so only a total time in <code>mpn_mul</code> would be
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accumulated, not a separate amount for each call site.
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</p>
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<p>The x86 assembly code has support for this option, but on other processors
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the assembly routines will be as if compiled without ‘<samp>-pg</samp>’ and therefore
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not be included in the call counts.
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</p>
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<p>On x86 and m68k systems ‘<samp>-pg</samp>’ and ‘<samp>-fomit-frame-pointer</samp>’ are
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incompatible, so the latter is omitted from the default flags in that case,
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which might result in poorer code generation.
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</p>
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<p>Incidentally, it should be possible to use the <code>gprof</code> program with a
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plain ‘<samp>--enable-profiling=prof</samp>’ build. But in that case only the
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‘<samp>gprof -p</samp>’ flat profile and call counts can be expected to be valid, not
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the ‘<samp>gprof -q</samp>’ call graph.
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</p>
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</dd>
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<dt>‘<samp>--enable-profiling=instrument</samp>’</dt>
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<dd><a name="index-_002dfinstrument_002dfunctions"></a>
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<a name="index-instrument_002dfunctions"></a>
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<p>Build with the GCC option ‘<samp>-finstrument-functions</samp>’ added to the
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‘<samp>CFLAGS</samp>’ (see <a href="http://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#Code-Gen-Options">Options for Code Generation</a> in <cite>Using the GNU Compiler Collection (GCC)</cite>).
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</p>
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<p>This inserts special instrumenting calls at the start and end of each
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function, allowing exact timing and full call graph construction.
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</p>
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<p>This instrumenting is not normally a standard system feature and will require
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support from an external library, such as
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</p>
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<a name="index-FunctionCheck"></a>
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<a name="index-fnccheck"></a>
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<div class="display">
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<pre class="display"><a href="http://sourceforge.net/projects/fnccheck/">http://sourceforge.net/projects/fnccheck/</a>
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</pre></div>
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<p>This should be included in ‘<samp>LIBS</samp>’ during the GMP configure so that test
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programs will link. For example,
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</p>
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<div class="example">
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<pre class="example">./configure --enable-profiling=instrument LIBS=-lfc
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</pre></div>
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<p>On a GNU system the C library provides dummy instrumenting functions, so
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programs compiled with this option will link. In this case it’s only
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necessary to ensure the correct library is added when linking an application.
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</p>
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<p>The x86 assembly code supports this option, but on other processors the
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assembly routines will be as if compiled without
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‘<samp>-finstrument-functions</samp>’ meaning time spent in them will effectively be
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attributed to their caller.
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Autoconf.html#Autoconf" accesskey="n" rel="next">Autoconf</a>, Previous: <a href="Debugging.html#Debugging" accesskey="p" rel="prev">Debugging</a>, Up: <a href="GMP-Basics.html#GMP-Basics" accesskey="u" rel="up">GMP Basics</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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