parallel-processing - OpenMP:如何使循环分配仅取决于数组大小？

Question

考虑以下代码块:

int array[30000]

#pragma omp parallel
{
   for( int a = 0; a < 1000; a++ )
   {
       #pragma omp for nowait
       for( int i = 0; i < 30000; i++ )
       {
           /*calculations with array[i] and also other array entries happen here*/
       }
   }
}

竞态条件在我的应用程序中不是问题，但我想强制并行区域中的每个线程处理 正是 每次通过内部 for 循环运行相同的数组 block 。

据我了解， schedule(static) 根据线程数和数组长度分配 for 循环项。然而，对于不同循环或同一循环的不同重复(即使线程数和长度相同)，分布是否会发生变化尚不清楚。

标准对此有何评论？ schedule(static) 是否足以强制执行此操作？

Answer 1

我相信这句话来自 OpenMP Specification提供这样的保证:

A compliant implementation of the static schedule must ensure that the same assignment of logical iteration numbers to threads will be used in two worksharing-loop regions if the following conditions are satisfied: 1) both worksharing-loop regions have the same number of loop iterations, 2) both worksharing-loop regions have the same value of chunk_size specified, or both worksharing-loop regions have no chunk_size specified, 3) both worksharing-loop regions bind to the same parallel region, and 4) neither loop is associated with a SIMD construct.