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<title>avram - a virtual machine code interpreter: 2.7.7.3 Profile</title>

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<a name="Profile"></a>
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<hr size="1">
<a name="Profile-1"></a>
<h4 class="subsubsection">2.7.7.3 Profile</h4>

<p>The virtual machine supports a profiling capability by way of this
<a name="index-profile_002etxt-1"></a>
feature. Profiling an application causes run time statistics about it to
be written to a file &lsquo;<tt>./profile.txt</tt>&rsquo;. Profiled applications are of
the form indicated in the following theorem
</p>
<dl compact="compact">
<dt> <em>T12</em></dt>
<dd><p>[[<code>profile</code>]] <code>(<var>f</var>,<var>s</var>)</code> = <code>((nil,nil),((nil,nil),(nil,((<var>f</var>,<var>s</var>),nil))))</code>
</p></dd>
</dl>

<p>where <code><var>f</var></code> stands for the virtual code of the application, and
<code><var>s</var></code> 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> <code><var>f</var></code>.
</p>
<dl compact="compact">
<dt> <em>P9</em></dt>
<dd><p>([[<code>profile</code>]] <code>(<var>f</var>,<var>s</var>)</code>) <code><var>x</var></code> = <code><var>f</var> <var>x</var></code>
</p></dd>
</dl>

<p>Unlike the situation with <code>note</code>, the annotation <code><var>s</var></code> of
<a name="index-note-1"></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
&lsquo;<tt>./profile.txt</tt>&rsquo;. Ordinarily this string will be the source code
identifier of the function being profiled.
</p>
<p>When profiles are used in many parts of an application, an informative
table is generated showing the time spent in each part.
</p>
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