如何在openMP的单个区域内并行for循环? [英] How to parallel for loop inside single region in openMP?

问题描述

我有一个递归程序，我想使用openMP来加快速度.结构如下.

I have a recursive program which I want to speed up using openMP. The structure is like below.

我不熟悉omp task，只是从这里学到了一些东西.看来我必须将buildTree包装在omp single区域中.

I am not familiar with omp task and just learnt something from here. It seems that I have to wrap buildTree in a omp single region.

但是，我也想并行化buildTree中的for循环，如何实现呢?

However, I also want to parallelize the for loop inside buildTree, how can I achieve that?

int main()
{
    #pragma omp parallel 
    {
        #pragma omp single nowait
        buildTree();
    }
}
void buildTree
{
    if(endRecursion)
        return;
    for(int i = 0; i < problemSize; i++)
    {
        // I want to parallelize these code using omp for
    }

    if(problemSizeIsSmall)
    {
        buildTree(subProblemSize); // left subtree
        buildTree(subProblemSize); // right subtree
    }
    else
    {
        #pragma omp task
        {
            buildTree(subProblemSize); // left subtree
        }
        #pragma omp task
        {
            buildTree(subProblemSize); // right subtree
        }
    }
}

推荐答案

我认为您可以使用

I think you can use nested parallelism in your problem. Your code would look like this way in your main():

#pragma omp parallel for num_threads(2)
buildTree();

和buildTree()中的

omp_set_num_threads(4); // 4 or whatever number of threads you want
#pragma omp parallel for 
for(int i = 0; i < problemSize; i++)

检查我的第4.3节Example 4–2 Calls to OpenMP Routines Within Parallel Regions链接以获取更多详细信息

Check the section 4.3 Example 4–2 Calls to OpenMP Routines Within Parallel Regions of my first link for more details

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