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<title>The GNU Fortran Compiler: ATOMIC_CAS</title>
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<a name="ATOMIC_005fCAS"></a>
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<p>
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Next: <a href="ATOMIC_005fDEFINE.html#ATOMIC_005fDEFINE" accesskey="n" rel="next">ATOMIC_DEFINE</a>, Previous: <a href="ATOMIC_005fAND.html#ATOMIC_005fAND" accesskey="p" rel="prev">ATOMIC_AND</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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<a name="ATOMIC_005fCAS-_002d_002d_002d-Atomic-compare-and-swap"></a>
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<h3 class="section">9.26 <code>ATOMIC_CAS</code> — Atomic compare and swap</h3>
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<a name="index-ATOMIC_005fDEFINE"></a>
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<a name="index-Atomic-subroutine_002c-compare-and-swap"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p><code>ATOMIC_CAS</code> compares the variable <var>ATOM</var> with the value of
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<var>COMPARE</var>; if the value is the same, <var>ATOM</var> is set to the value
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of <var>NEW</var>. Additionally, <var>OLD</var> is set to the value of <var>ATOM</var>
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that was used for the comparison. When <var>STAT</var> is present and the invokation
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was successful, it is assigned the value 0. If it is present and the invokation
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has failed, it is assigned a positive value; in particular, for a coindexed
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<var>ATOM</var>, if the remote image has stopped, it is assigned the value of
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<code>ISO_FORTRAN_ENV</code>’s <code>STAT_STOPPED_IMAGE</code> and if the remote image has
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failed, the value <code>STAT_FAILED_IMAGE</code>.
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</p>
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</dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>TS 18508 or later
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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>Atomic subroutine
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><p><code>CALL ATOMIC_CAS (ATOM, OLD, COMPARE, NEW [, STAT])</code>
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</p>
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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>ATOM</var></td><td width="70%">Scalar coarray or coindexed variable of either integer
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type with <code>ATOMIC_INT_KIND</code> kind or logical type with
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<code>ATOMIC_LOGICAL_KIND</code> kind.</td></tr>
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<tr><td width="15%"><var>OLD</var></td><td width="70%">Scalar of the same type and kind as <var>ATOM</var>.</td></tr>
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<tr><td width="15%"><var>COMPARE</var></td><td width="70%">Scalar variable of the same type and kind as
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<var>ATOM</var>.</td></tr>
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<tr><td width="15%"><var>NEW</var></td><td width="70%">Scalar variable of the same type as <var>ATOM</var>. If kind
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is different, the value is converted to the kind of <var>ATOM</var>.</td></tr>
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<tr><td width="15%"><var>STAT</var></td><td width="70%">(optional) Scalar default-kind integer variable.</td></tr>
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</table>
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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 atomic
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use iso_fortran_env
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logical(atomic_logical_kind) :: atom[*], prev
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call atomic_cas (atom[1], prev, .false., .true.))
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end program atomic
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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="ATOMIC_005fDEFINE.html#ATOMIC_005fDEFINE">ATOMIC_DEFINE</a>, <a href="ATOMIC_005fREF.html#ATOMIC_005fREF">ATOMIC_REF</a>, <a href="ISO_005fFORTRAN_005fENV.html#ISO_005fFORTRAN_005fENV">ISO_FORTRAN_ENV</a>
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</p></dd>
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