openmp并行for循环，具有两个或多个减少 [英] openmp parallel for loop with two or more reductions

问题描述

您好，我想知道这是否是进行常规for循环但有两个简化的正确方法，这是下面的正确方法吗?这项工作是否也可以进行两次以上的简化.有一个更好的方法吗? 还有机会将其与MPI_ALLREDUCE命令集成吗?

Hi just wondering if this is the right way to go going about having a regular for loop but with two reductions , is this the right approach below? Would this work with more then two reductions as well. Is there a better way to do this? also is there any chance to integrate this with an MPI_ALLREDUCE command?

heres the psuedo code

      #pragma omp parallel for \
      default(shared) private(i) \
      //todo first  reduction(+:sum)
      //todo second reduction(+:result)

      for loop i < n; i ++; {
        y = fun(x,z,i)
        sum += fun2(y,x)
        result += fun3(y,z)
      }

推荐答案

您可以通过指定多个以逗号分隔的变量(即列表)来简化操作:

You can do reduction by specifying more than one variable separated by a comma, i.e. a list:

#pragma omp parallel for default(shared) reduction(+:sum,result) ...

将为sum和result创建专用线程变量，这些变量将使用+组合在一起，并在线程块的末尾分配给原始全局变量.

Private thread variables will be created for sum and result that will be combined using + and assigned to the original global variables at the end of the thread block.

此外，变量y应该标记为私有.

Also, variable y should be marked private.

请参见 https://computing.llnl.gov/tutorials/openMP/#REDUCTION

这篇关于openmp并行for循环，具有两个或多个减少的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！