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| <title>GNU gprof: How do I?</title> |
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| <a name="How-do-I_003f"></a> |
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| Next: <a href="Incompatibilities.html#Incompatibilities" accesskey="n" rel="next">Incompatibilities</a>, Previous: <a href="Inaccuracy.html#Inaccuracy" accesskey="p" rel="prev">Inaccuracy</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> |
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| <a name="Answers-to-Common-Questions"></a> |
| <h2 class="chapter">7 Answers to Common Questions</h2> |
| |
| <dl compact="compact"> |
| <dt>How can I get more exact information about hot spots in my program?</dt> |
| <dd> |
| <p>Looking at the per-line call counts only tells part of the story. |
| Because <code>gprof</code> can only report call times and counts by function, |
| the best way to get finer-grained information on where the program |
| is spending its time is to re-factor large functions into sequences |
| of calls to smaller ones. Beware however that this can introduce |
| artificial hot spots since compiling with ‘<samp>-pg</samp>’ adds a significant |
| overhead to function calls. An alternative solution is to use a |
| non-intrusive profiler, e.g. oprofile. |
| </p> |
| </dd> |
| <dt>How do I find which lines in my program were executed the most times?</dt> |
| <dd> |
| <p>Use the <code>gcov</code> program. |
| </p> |
| </dd> |
| <dt>How do I find which lines in my program called a particular function?</dt> |
| <dd> |
| <p>Use ‘<samp>gprof -l</samp>’ and lookup the function in the call graph. |
| The callers will be broken down by function and line number. |
| </p> |
| </dd> |
| <dt>How do I analyze a program that runs for less than a second?</dt> |
| <dd> |
| <p>Try using a shell script like this one: |
| </p> |
| <div class="example"> |
| <pre class="example">for i in `seq 1 100`; do |
| fastprog |
| mv gmon.out gmon.out.$i |
| done |
| |
| gprof -s fastprog gmon.out.* |
| |
| gprof fastprog gmon.sum |
| </pre></div> |
| |
| <p>If your program is completely deterministic, all the call counts |
| will be simple multiples of 100 (i.e., a function called once in |
| each run will appear with a call count of 100). |
| </p> |
| </dd> |
| </dl> |
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