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<h3 class="section">13.6 Profiling</h3>
<p><a name="index-profiler-868"></a><a name="index-code-profiling-869"></a>
Octave supports profiling of code execution on a per-function level. If
profiling is enabled, each call to a function (supporting built-ins,
operators, functions in oct- and mex-files, user-defined functions in
Octave code and anonymous functions) is recorded while running Octave
code. After that, this data can aid in analyzing the code behavior, and
is in particular helpful for finding “hot spots” in the code which use
up a lot of computation time and are the best targets to spend
optimization efforts on.
<p>The main command for profiling is <code>profile</code>, which can be used to
start or stop the profiler and also to query collected data afterwards.
The data is returned in an Octave data structure which can then be
examined or further processed by other routines or tools.
<!-- profile scripts/general/profile.m -->
<p><a name="doc_002dprofile"></a>
<div class="defun">
— Command: <b>profile</b><var> on<a name="index-profile-870"></a></var><br>
— Command: <b>profile</b><var> off<a name="index-profile-871"></a></var><br>
— Command: <b>profile</b><var> resume<a name="index-profile-872"></a></var><br>
— Command: <b>profile</b><var> clear<a name="index-profile-873"></a></var><br>
— Function File: <var>S</var> = <b>profile</b> (<var>'status'</var>)<var><a name="index-profile-874"></a></var><br>
— Function File: <var>T</var> = <b>profile</b> (<var>'info'</var>)<var><a name="index-profile-875"></a></var><br>
<blockquote><p>Control the built-in profiler.
<dl>
<dt><code>profile on</code><dd>Start the profiler, clearing all previously collected data if there
is any.
<br><dt><code>profile off</code><dd>Stop profiling. The collected data can later be retrieved and examined
with calls like <code>S = profile ('info')</code>.
<br><dt><code>profile clear</code><dd>Clear all collected profiler data.
<br><dt><code>profile resume</code><dd>Restart profiling without cleaning up the old data and instead
all newly collected statistics are added to the already existing ones.
<br><dt><var>S</var><code> = profile ('status')</code><dd>Return a structure filled with certain information about the current status
of the profiler. At the moment, the only field is <code>ProfilerStatus</code>
which is either 'on' or 'off'.
<br><dt><var>T</var><code> = profile ('info')</code><dd>Return the collected profiling statistics in the structure <var>T</var>.
The flat profile is returned in the field <code>FunctionTable</code> which is an
array of structures, each entry corresponding to a function which was called
and for which profiling statistics are present. Furthermore, the field
<code>Hierarchical</code> contains the hierarchical call-tree. Each node
has an index into the <code>FunctionTable</code> identifying the function it
corresponds to as well as data fields for number of calls and time spent
at this level in the call-tree.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dprofshow.html#doc_002dprofshow">profshow</a>, <a href="doc_002dprofexplore.html#doc_002dprofexplore">profexplore</a>.
</dl>
</p></blockquote></div>
<p>An easy way to get an overview over the collected data is
<code>profshow</code>. This function takes the profiler data returned by
<code>profile</code> as input and prints a flat profile, for instance:
<pre class="example"> Function Attr Time (s) Calls
----------------------------------------
>myfib R 2.195 13529
binary <= 0.061 13529
binary - 0.050 13528
binary + 0.026 6764
</pre>
<p>This shows that most of the run time was spent executing the function
‘<samp><span class="samp">myfib</span></samp>’, and some minor proportion evaluating the listed binary
operators. Furthermore, it is shown how often the function was called
and the profiler also records that it is recursive.
<!-- profshow scripts/general/profshow.m -->
<p><a name="doc_002dprofshow"></a>
<div class="defun">
— Function File: <b>profshow</b> (<var>data</var>)<var><a name="index-profshow-876"></a></var><br>
— Function File: <b>profshow</b> (<var>data, n</var>)<var><a name="index-profshow-877"></a></var><br>
<blockquote><p>Show flat profiler results.
<p>This command prints out profiler data as a flat profile. <var>data</var> is the
structure returned by <code>profile ('info')</code>. If <var>n</var> is given, it
specifies the number of functions to show in the profile; functions are
sorted in descending order by total time spent in them. If there are more
than <var>n</var> included in the profile, those will not be shown. <var>n</var>
defaults to 20.
<p>The attribute column shows ‘<samp><span class="samp">R</span></samp>’ for recursive functions and nothing
otherwise.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dprofexplore.html#doc_002dprofexplore">profexplore</a>, <a href="doc_002dprofile.html#doc_002dprofile">profile</a>.
</p></blockquote></div>
<!-- profexplore scripts/general/profexplore.m -->
<p><a name="doc_002dprofexplore"></a>
<div class="defun">
— Function File: <b>profexplore</b> (<var>data</var>)<var><a name="index-profexplore-878"></a></var><br>
<blockquote><p>Interactively explore hierarchical profiler output.
<p>Assuming <var>data</var> is the structure with profile data returned by
<code>profile ('info')</code>, this command opens an interactive prompt
that can be used to explore the call-tree. Type <kbd>help</kbd> to get a list
of possible commands.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dprofile.html#doc_002dprofile">profile</a>, <a href="doc_002dprofshow.html#doc_002dprofshow">profshow</a>.
</p></blockquote></div>
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