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| <h3 class="section">4.10 Implementing PARALLEL construct</h3> |
| |
| <div class="smallexample"> |
| <pre class="smallexample"> #pragma omp parallel |
| { |
| body; |
| } |
| </pre></div> |
| |
| <p>becomes |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"> void subfunction (void *data) |
| { |
| use data; |
| body; |
| } |
| |
| setup data; |
| GOMP_parallel_start (subfunction, &data, num_threads); |
| subfunction (&data); |
| GOMP_parallel_end (); |
| </pre></div> |
| |
| <div class="smallexample"> |
| <pre class="smallexample"> void GOMP_parallel_start (void (*fn)(void *), void *data, unsigned num_threads) |
| </pre></div> |
| |
| <p>The <var>FN</var> argument is the subfunction to be run in parallel. |
| </p> |
| <p>The <var>DATA</var> argument is a pointer to a structure used to |
| communicate data in and out of the subfunction, as discussed |
| above with respect to FIRSTPRIVATE et al. |
| </p> |
| <p>The <var>NUM_THREADS</var> argument is 1 if an IF clause is present |
| and false, or the value of the NUM_THREADS clause, if |
| present, or 0. |
| </p> |
| <p>The function needs to create the appropriate number of |
| threads and/or launch them from the dock. It needs to |
| create the team structure and assign team ids. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"> void GOMP_parallel_end (void) |
| </pre></div> |
| |
| <p>Tears down the team and returns us to the previous <code>omp_in_parallel()</code> state. |
| </p> |
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