在Fortran中获取OpenMP线程中的最大值 [英] Get the maximum value among OpenMP threads in Fortran

问题描述

我有一个do循环，该循环更新T值并计算迭代期间的最大差异，称为dumax.

I have a do loop which updates T value and calculates the maximum difference during the iteration, called dumax.

我需要初始化dumax，因此将其设置为

I need to initialize dumax, so I set it to be

firstprivate

然后我将无法使用:

reduction(max: dumax)

归约运算符似乎接受私有变量. 那么在结束并行操作之前如何获得dumax的最大值?

Reduction operator seems to accept private variable. Then how can I get the maximum value of dumax before I end the parallel?

我的程序如下所示:

DUMAX=0.0D0
!$OMP PARALLEL DEFAULT(PRIVATE), SHARED(T_R, T_B), FIRSTPRIVATE(DUMAX)
            !$OMP DO 
            DO I=2, N-1, 2
                DO J=2, N-1, 2
                    T_OLD=T_B(I,J)
                    T_B(I,J)=0.25*(T_R(I,J-1)+T_R(I,J+1)+T_R(I+1,J)+&
                                    T_R(I-1,J)-DX**2*S(I,J))
                    DUMAX=MAX(DUMAX, ABS(T_OLD-T_B(I,J)))
                END DO
            END DO
            !$OMP END DO 
!$OMP END PARALLEL

推荐答案

您不应将dumax设置为firstprivate.归约变量应为shared.使其共享，然后使用reduction(max: dumax).您的初始化将保留.

You should not set dumax to firstprivate. Reduction variables should be shared. Make it shared and then use reduction(max: dumax). Your initialization will be kept.

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