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88 lines
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<title>How do I? - GNU gprof</title>
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<link rel="prev" href="Inaccuracy.html#Inaccuracy" title="Inaccuracy">
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This file documents the gprof profiler of the GNU system.
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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<div class="node">
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<a name="How-do-I%3f"></a>
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<a name="How-do-I_003f"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Incompatibilities.html#Incompatibilities">Incompatibilities</a>,
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Previous: <a rel="previous" accesskey="p" href="Inaccuracy.html#Inaccuracy">Inaccuracy</a>,
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Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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<hr>
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</div>
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<h2 class="chapter">7 Answers to Common Questions</h2>
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<dl>
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<dt>How can I get more exact information about hot spots in my program?<dd>
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Looking at the per-line call counts only tells part of the story.
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Because <code>gprof</code> can only report call times and counts by function,
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the best way to get finer-grained information on where the program
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is spending its time is to re-factor large functions into sequences
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of calls to smaller ones. Beware however that this can introduce
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artificial hot spots since compiling with ‘<samp><span class="samp">-pg</span></samp>’ adds a significant
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overhead to function calls. An alternative solution is to use a
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non-intrusive profiler, e.g. oprofile.
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<br><dt>How do I find which lines in my program were executed the most times?<dd>
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Use the <code>gcov</code> program.
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<br><dt>How do I find which lines in my program called a particular function?<dd>
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Use ‘<samp><span class="samp">gprof -l</span></samp>’ and lookup the function in the call graph.
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The callers will be broken down by function and line number.
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<br><dt>How do I analyze a program that runs for less than a second?<dd>
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Try using a shell script like this one:
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<pre class="example"> for i in `seq 1 100`; do
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fastprog
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mv gmon.out gmon.out.$i
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done
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gprof -s fastprog gmon.out.*
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gprof fastprog gmon.sum
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</pre>
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<p>If your program is completely deterministic, all the call counts
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will be simple multiples of 100 (i.e., a function called once in
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each run will appear with a call count of 100).
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</dl>
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</body></html>
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