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184 lines
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<head>
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<title>The GNU Fortran Compiler: DTIME</title>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="DTIME"></a>
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<div class="header">
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<p>
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Next: <a href="EOSHIFT.html#EOSHIFT" accesskey="n" rel="next">EOSHIFT</a>, Previous: <a href="DSHIFTR.html#DSHIFTR" accesskey="p" rel="prev">DSHIFTR</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="DTIME-_002d_002d_002d-Execution-time-subroutine-_0028or-function_0029"></a>
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<h3 class="section">9.85 <code>DTIME</code> — Execution time subroutine (or function)</h3>
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<a name="index-DTIME"></a>
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<a name="index-time_002c-elapsed-1"></a>
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<a name="index-elapsed-time"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p><code>DTIME(VALUES, TIME)</code> initially returns the number of seconds of runtime
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since the start of the process’s execution in <var>TIME</var>. <var>VALUES</var>
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returns the user and system components of this time in <code>VALUES(1)</code> and
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<code>VALUES(2)</code> respectively. <var>TIME</var> is equal to <code>VALUES(1) +
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VALUES(2)</code>.
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</p>
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<p>Subsequent invocations of <code>DTIME</code> return values accumulated since the
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previous invocation.
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</p>
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<p>On some systems, the underlying timings are represented using types with
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sufficiently small limits that overflows (wrap around) are possible, such as
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32-bit types. Therefore, the values returned by this intrinsic might be, or
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become, negative, or numerically less than previous values, during a single
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run of the compiled program.
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</p>
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<p>Please note, that this implementation is thread safe if used within OpenMP
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directives, i.e., its state will be consistent while called from multiple
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threads. However, if <code>DTIME</code> is called from multiple threads, the result
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is still the time since the last invocation. This may not give the intended
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results. If possible, use <code>CPU_TIME</code> instead.
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</p>
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<p>This intrinsic is provided in both subroutine and function forms; however,
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only one form can be used in any given program unit.
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</p>
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<p><var>VALUES</var> and <var>TIME</var> are <code>INTENT(OUT)</code> and provide the following:
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</p>
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<table>
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<tr><td width="15%"></td><td width="30%"><code>VALUES(1)</code>:</td><td width="40%">User time in seconds.</td></tr>
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<tr><td width="15%"></td><td width="30%"><code>VALUES(2)</code>:</td><td width="40%">System time in seconds.</td></tr>
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<tr><td width="15%"></td><td width="30%"><code>TIME</code>:</td><td width="40%">Run time since start in seconds.</td></tr>
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</table>
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</dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>GNU extension
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</p>
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</dd>
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<dt><em>Class</em>:</dt>
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<dd><p>Subroutine, function
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><table>
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<tr><td width="80%"><code>CALL DTIME(VALUES, TIME)</code>.</td></tr>
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<tr><td width="80%"><code>TIME = DTIME(VALUES)</code>, (not recommended).</td></tr>
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</table>
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</dd>
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<dt><em>Arguments</em>:</dt>
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<dd><table>
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<tr><td width="15%"><var>VALUES</var></td><td width="70%">The type shall be <code>REAL(4), DIMENSION(2)</code>.</td></tr>
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<tr><td width="15%"><var>TIME</var></td><td width="70%">The type shall be <code>REAL(4)</code>.</td></tr>
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</table>
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</dd>
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<dt><em>Return value</em>:</dt>
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<dd><p>Elapsed time in seconds since the last invocation or since the start of program
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execution if not called before.
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</p>
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</dd>
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<dt><em>Example</em>:</dt>
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<dd><div class="smallexample">
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<pre class="smallexample">program test_dtime
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integer(8) :: i, j
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real, dimension(2) :: tarray
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real :: result
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call dtime(tarray, result)
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print *, result
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print *, tarray(1)
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print *, tarray(2)
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do i=1,100000000 ! Just a delay
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j = i * i - i
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end do
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call dtime(tarray, result)
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print *, result
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print *, tarray(1)
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print *, tarray(2)
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end program test_dtime
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</pre></div>
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</dd>
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<dt><em>See also</em>:</dt>
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<dd><p><a href="CPU_005fTIME.html#CPU_005fTIME">CPU_TIME</a>
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="EOSHIFT.html#EOSHIFT" accesskey="n" rel="next">EOSHIFT</a>, Previous: <a href="DSHIFTR.html#DSHIFTR" accesskey="p" rel="prev">DSHIFTR</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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