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<title>The GNU Fortran Compiler: DTIME</title>

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<hr>
<a name="DTIME-_002d_002d_002d-Execution-time-subroutine-_0028or-function_0029"></a>
<h3 class="section">9.92 <code>DTIME</code> &mdash; Execution time subroutine (or function)</h3>
<a name="index-DTIME"></a>
<a name="index-time_002c-elapsed-1"></a>
<a name="index-elapsed-time"></a>

<dl compact="compact">
<dt><em>Description</em>:</dt>
<dd><p><code>DTIME(VALUES, TIME)</code> initially returns the number of seconds of runtime
since the start of the process&rsquo;s execution in <var>TIME</var>.  <var>VALUES</var>
returns the user and system components of this time in <code>VALUES(1)</code> and
<code>VALUES(2)</code> respectively. <var>TIME</var> is equal to <code>VALUES(1) +
VALUES(2)</code>.
</p>
<p>Subsequent invocations of <code>DTIME</code> return values accumulated since the
previous invocation.
</p>
<p>On some systems, the underlying timings are represented using types with
sufficiently small limits that overflows (wrap around) are possible, such as
32-bit types. Therefore, the values returned by this intrinsic might be, or
become, negative, or numerically less than previous values, during a single
run of the compiled program.
</p>
<p>Please note, that this implementation is thread safe if used within OpenMP
directives, i.e., its state will be consistent while called from multiple
threads. However, if <code>DTIME</code> is called from multiple threads, the result
is still the time since the last invocation. This may not give the intended
results. If possible, use <code>CPU_TIME</code> instead.
</p>
<p>This intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
</p>
<p><var>VALUES</var> and <var>TIME</var> are <code>INTENT(OUT)</code> and provide the following:
</p>
<table>
<tr><td width="15%"></td><td width="30%"><code>VALUES(1)</code>:</td><td width="40%">User time in seconds.</td></tr>
<tr><td width="15%"></td><td width="30%"><code>VALUES(2)</code>:</td><td width="40%">System time in seconds.</td></tr>
<tr><td width="15%"></td><td width="30%"><code>TIME</code>:</td><td width="40%">Run time since start in seconds.</td></tr>
</table>

</dd>
<dt><em>Standard</em>:</dt>
<dd><p>GNU extension
</p>
</dd>
<dt><em>Class</em>:</dt>
<dd><p>Subroutine, function
</p>
</dd>
<dt><em>Syntax</em>:</dt>
<dd><table>
<tr><td width="80%"><code>CALL DTIME(VALUES, TIME)</code>.</td></tr>
<tr><td width="80%"><code>TIME = DTIME(VALUES)</code>, (not recommended).</td></tr>
</table>

</dd>
<dt><em>Arguments</em>:</dt>
<dd><table>
<tr><td width="15%"><var>VALUES</var></td><td width="70%">The type shall be <code>REAL(4), DIMENSION(2)</code>.</td></tr>
<tr><td width="15%"><var>TIME</var></td><td width="70%">The type shall be <code>REAL(4)</code>.</td></tr>
</table>

</dd>
<dt><em>Return value</em>:</dt>
<dd><p>Elapsed time in seconds since the last invocation or since the start of program
execution if not called before.
</p>
</dd>
<dt><em>Example</em>:</dt>
<dd><div class="smallexample">
<pre class="smallexample">program test_dtime
    integer(8) :: i, j
    real, dimension(2) :: tarray
    real :: result
    call dtime(tarray, result)
    print *, result
    print *, tarray(1)
    print *, tarray(2)   
    do i=1,100000000    ! Just a delay
        j = i * i - i
    end do
    call dtime(tarray, result)
    print *, result
    print *, tarray(1)
    print *, tarray(2)
end program test_dtime
</pre></div>

</dd>
<dt><em>See also</em>:</dt>
<dd><p><a href="CPU_005fTIME.html#CPU_005fTIME">CPU_TIME</a>
</p>
</dd>
</dl>


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