OpenMP和部分 [英] OpenMP and sections

问题描述

我有以下代码：

#pragma omp parallel sections num_threads(2) {
  #pragma omp section
   Function_1;
   #pragma omp section
   Function_2;
}

但在Function_1和Function_2中，我有一个并行线程，但只有一个线程运行。
那么，如何并行运行Function_1和Function_2并在这些函数中运行多个线程？

but within the Function_1 and Function_2, i have a parallel for but just one thread run it. So, how run the Function_1 and Function_2 in parallel and run several threads within these functions?

thx！

推荐答案

在另一个区域内有一个并行区域称为嵌套。默认情况下，嵌套区域是非活动的，这意味着它们连续执行。为了使其有效，您可以：

Having one parallel region inside another is called nesting. By default nested regions are inactive, which means that they execute serially. In order to make them active, you can:

• 设置环境变量 OMP_NESTED 到 true


• 在并行区域之前插入以下调用： code> omp_set_nested（1）;

• set the environment variable OMP_NESTED to true
• insert the following call before the enclosing parallel region: omp_set_nested(1);

还可以限制级别数，其中嵌套并行化工作原理：

One can also limit the number of levels, where nested parallelism works, by:

• 将环境变量 OMP_MAX_ACTIVE_LEVELS 设置为 num 或


• 呼叫 omp_set_max_active_levels（num）;

• setting the environment variable OMP_MAX_ACTIVE_LEVELS to num, or
• calling omp_set_max_active_levels(num);

其中 num 是所需的最大活动级别，例如值 3 会使所有并行区域，嵌套超过 3 级别深，无效。

where num is the desired maximum active level, e.g. a value of 3 would render all parallel regions, nested more than 3 levels deep, inactive.

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