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<h5 class="subsubsection">2.7.7.3 Profile</h5>

<p>The virtual machine supports a profiling capability by way of this
<a name="index-g_t_0040file_007bprofile_002etxt_007d-284"></a>feature. Profiling an application causes run time statistics about it to
be written to a file <samp><span class="file">./profile.txt</span></samp>. Profiled applications are of
the form indicated in the following theorem

     <dl>
<dt><em>T12</em><dd>[[<code>profile</code>]] <code>(</code><var>f</var><code>,</code><var>s</var><code>)</code> = <code>((nil,nil),((nil,nil),(nil,((</code><var>f</var><code>,</code><var>s</var><code>),nil))))</code>
</dl>

<p class="noindent">where <var>f</var> stands for the virtual code of the application, and
<var>s</var> stands for the name of it to be written to the file. 
The semantics of a profiled function is identical to the unprofiled
form for any non-<code>nil</code> <var>f</var>.

     <dl>
<dt><em>P9</em><dd>([[<code>profile</code>]] <code>(</code><var>f</var><code>,</code><var>s</var><code>)</code>) <var>x</var> = <var>f</var> <var>x</var>
</dl>

   <p>Unlike the situation with <code>note</code>, the annotation <var>s</var> of
<a name="index-g_t_0040code_007bnote_007d-285"></a>used in profiled code is not in an unrestricted format but must be a
character string in the standard representation (as in
<a href="Representation-of-Numeric-and-Textual-Data.html#Representation-of-Numeric-and-Textual-Data">Representation of Numeric and Textual Data</a>),
because this string needs to be written by <code>avram</code> to the file
<samp><span class="file">./profile.txt</span></samp>. Ordinarily this string will be the source code
identifier of the function being profiled.

   <p>When profiles are used in many parts of an application, an informative
table is generated showing the time spent in each part.

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