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<title>GNU libgomp: Implementing PARALLEL construct</title>
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Next: <a href="Implementing-FOR-construct.html#Implementing-FOR-construct" accesskey="n" rel="next">Implementing FOR construct</a>, Previous: <a href="Implementing-REDUCTION-clause.html#Implementing-REDUCTION-clause" accesskey="p" rel="prev">Implementing REDUCTION clause</a>, Up: <a href="The-libgomp-ABI.html#The-libgomp-ABI" accesskey="u" rel="up">The libgomp ABI</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Library-Index.html#Library-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Implementing-PARALLEL-construct-1"></a>
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<h3 class="section">9.10 Implementing PARALLEL construct</h3>
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<div class="smallexample">
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<pre class="smallexample"> #pragma omp parallel
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{
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body;
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}
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</pre></div>
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<p>becomes
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</p>
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<div class="smallexample">
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<pre class="smallexample"> void subfunction (void *data)
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{
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use data;
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body;
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}
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setup data;
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GOMP_parallel_start (subfunction, &data, num_threads);
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subfunction (&data);
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GOMP_parallel_end ();
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</pre></div>
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<div class="smallexample">
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<pre class="smallexample"> void GOMP_parallel_start (void (*fn)(void *), void *data, unsigned num_threads)
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</pre></div>
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<p>The <var>FN</var> argument is the subfunction to be run in parallel.
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</p>
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<p>The <var>DATA</var> argument is a pointer to a structure used to
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communicate data in and out of the subfunction, as discussed
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above with respect to FIRSTPRIVATE et al.
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</p>
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<p>The <var>NUM_THREADS</var> argument is 1 if an IF clause is present
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and false, or the value of the NUM_THREADS clause, if
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present, or 0.
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</p>
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<p>The function needs to create the appropriate number of
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threads and/or launch them from the dock. It needs to
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create the team structure and assign team ids.
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</p>
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<div class="smallexample">
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<pre class="smallexample"> void GOMP_parallel_end (void)
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</pre></div>
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<p>Tears down the team and returns us to the previous <code>omp_in_parallel()</code> state.
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</p>
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