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POSpecific thread order in C using GCC and OMP
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  1. POSpecific thread order in C using GCC and OMP
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    copied!<p>I need to make 4 teams with 4 threads each one with contiguous processors. </p> <p>The result I'm expecting is, for example:</p> <pre><code>Team 0 Thread 0 Processor: 0 Team 0 Thread 1 Processor: 1 Team 0 Thread 2 Processor: 2 Team 0 Thread 3 Processor: 3 Team 1 Thread 0 Processor: 4 Team 1 Thread 1 Processor: 5 Team 1 Thread 2 Processor: 6 Team 1 Thread 3 Processor: 7 Team 2 Thread 0 Processor: 8 Team 2 Thread 1 Processor: 9 Team 2 Thread 2 Processor: 10 Team 2 Thread 3 Processor: 11 Team 3 Thread 0 Processor: 12 Team 3 Thread 1 Processor: 13 Team 3 Thread 2 Processor: 14 Team 3 Thread 3 Processor: 15 </code></pre> <p>I can handle Processor Affinity in GCC using the GOMP_CPU_AFFINITY variable.</p> <p>I'm using:</p> <pre><code>#pragma omp parallel num_threads(4) </code></pre> <p>twice in order to get 2 fork levels.</p> <p>At the moment I'm having this order in GOMP_CPU_AFFINITY:</p> <pre><code>0 4 8 12 1 2 3 5 6 7 9 10 11 13 14 15 </code></pre> <p>So the first fork, the "fathers fork", gets:</p> <pre><code>Team 0 Thread 0 Processor: 0 Team 1 Thread 0 Processor: 4 Team 2 Thread 0 Processor: 8 Team 3 Thread 0 Processor: 12 </code></pre> <p>The problem I'm having is that the second group of forks make without any order so, for example I could have this situation (I'm using #pragma omp atomic so only one 'father' can ask for more processors at any time):</p> <pre><code>Team 0 Thread 0 Processor: 0 Team 0 Thread 1 Processor: 5 Team 0 Thread 2 Processor: 6 Team 0 Thread 3 Processor: 7 Team 1 Thread 0 Processor: 4 Team 1 Thread 1 Processor: 13 Team 1 Thread 2 Processor: 14 Team 1 Thread 3 Processor: 15 Team 2 Thread 0 Processor: 8 Team 2 Thread 1 Processor: 1 Team 2 Thread 2 Processor: 2 Team 2 Thread 3 Processor: 3 Team 3 Thread 0 Processor: 12 Team 3 Thread 1 Processor: 9 Team 3 Thread 2 Processor: 10 Team 3 Thread 3 Processor: 11 </code></pre> <p>The question is: Is there any way to make this second petition in order? </p> <p>I think I would have to make some sinchronization method with locks or something... </p> <p>Thanks in advance!</p> <ul> <li>Javier</li> </ul>
 

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