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<h3 class="section">8.55 <code>CPU_TIME</code> — CPU elapsed time in seconds</h3>
<p><a name="index-CPU_005fTIME-527"></a><a name="index-time_002c-elapsed-528"></a>
<dl>
<dt><em>Description</em>:<dd>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>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>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.
<br><dt><em>Standard</em>:<dd>Fortran 95 and later
<br><dt><em>Class</em>:<dd>Subroutine
<br><dt><em>Syntax</em>:<dd><code>CALL CPU_TIME(TIME)</code>
<br><dt><em>Arguments</em>:<dd>
<p><table summary=""><tr align="left"><td valign="top" width="15%"><var>TIME</var> </td><td valign="top" width="70%">The type shall be <code>REAL</code> with <code>INTENT(OUT)</code>.
<br></td></tr></table>
<br><dt><em>Return value</em>:<dd>None
<br><dt><em>Example</em>:<dd>
<pre class="smallexample"> program test_cpu_time
real :: start, finish
call cpu_time(start)
! put code to test here
call cpu_time(finish)
print '("Time = ",f6.3," seconds.")',finish-start
end program test_cpu_time
</pre>
<br><dt><em>See also</em>:<dd><a href="SYSTEM_005fCLOCK.html#SYSTEM_005fCLOCK">SYSTEM_CLOCK</a>, <a href="DATE_005fAND_005fTIME.html#DATE_005fAND_005fTIME">DATE_AND_TIME</a>
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