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<title>The GNU Fortran Compiler: CPU_TIME</title>
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<a name="CPU_005fTIME-_002d_002d_002d-CPU-elapsed-time-in-seconds"></a>
<h3 class="section">8.58 <code>CPU_TIME</code> &mdash; CPU elapsed time in seconds</h3>
<a name="index-CPU_005fTIME"></a>
<a name="index-time_002c-elapsed"></a>
<dl compact="compact">
<dt><em>Description</em>:</dt>
<dd><p>Returns a <code>REAL</code> value representing the elapsed CPU time in
seconds. This is useful for testing segments of code to determine
execution time.
</p>
<p>If a time source is available, time will be reported with microsecond
resolution. If no time source is available, <var>TIME</var> is set to
<code>-1.0</code>.
</p>
<p>Note that <var>TIME</var> may contain a, system dependent, arbitrary offset
and may not start with <code>0.0</code>. For <code>CPU_TIME</code>, the absolute
value is meaningless, only differences between subsequent calls to
this subroutine, as shown in the example below, should be used.
</p>
</dd>
<dt><em>Standard</em>:</dt>
<dd><p>Fortran 95 and later
</p>
</dd>
<dt><em>Class</em>:</dt>
<dd><p>Subroutine
</p>
</dd>
<dt><em>Syntax</em>:</dt>
<dd><p><code>CALL CPU_TIME(TIME)</code>
</p>
</dd>
<dt><em>Arguments</em>:</dt>
<dd><table>
<tr><td width="15%"><var>TIME</var></td><td width="70%">The type shall be <code>REAL</code> with <code>INTENT(OUT)</code>.</td></tr>
</table>
</dd>
<dt><em>Return value</em>:</dt>
<dd><p>None
</p>
</dd>
<dt><em>Example</em>:</dt>
<dd><div class="smallexample">
<pre class="smallexample">program test_cpu_time
real :: start, finish
call cpu_time(start)
! put code to test here
call cpu_time(finish)
print '(&quot;Time = &quot;,f6.3,&quot; seconds.&quot;)',finish-start
end program test_cpu_time
</pre></div>
</dd>
<dt><em>See also</em>:</dt>
<dd><p><a href="SYSTEM_005fCLOCK.html#SYSTEM_005fCLOCK">SYSTEM_CLOCK</a>, <a href="DATE_005fAND_005fTIME.html#DATE_005fAND_005fTIME">DATE_AND_TIME</a>
</p></dd>
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