CODEWITHSUNDEEP
fortranopenmpfortran77
Jovi DSilva
Jovi DSilva

Reputation: 226

Best way to parallelize this loop in OpenMP

I have the following loop which i have attempted to parallelized using OpenMP but i am seeing no performance improvement, can any one please suggest how to improve it.

thread = omp_get_max_threads ( )
chunk=jmaxm/thread
c$omp parallel shared (zetun,zetvn) private (i, j)
c$omp do schedule(DYNAMIC,chunk) ORDERED
    do j=2,jmaxm
        jm=j-1
        jp=j+1
             do i=2,imaxm
                if (rmask(i,j).eq.1.0)then
             im=i-1
             ip=i+1
             zetun(i,j)=
           +  (un(im,j,km)+un(ip,j,km)-2.*un(i,j,km))*recdx2
           +  + ((un(i,jp,km)-un(i,j,km))-
           +  (un(i,j,km)-un(i,jm,km)))*recdy2

             zetvn(i,j)=
           +  ((vn(ip,j,km)-vn(i,j,km))-
           +  (vn(i,j,km)-vn(im,j,km)))*recdx2
           +  + (vn(i,jp,km)+vn(i,jm,km)-2.*vn(i,j,km))*recdy2
              endif

        end do

    end do
 c$omp end do nowait
 c$omp end parallel

I am now adding the modified code it as follows, but still does not seem to make any improvement MODIFIED CODE:

  c$omp parallel shared (zetun,zetvn) private (i,j,jm,jp,im,ip,km)

  c$omp do schedule(DYNAMIC,20) 
   do j=2,jmaxm
        jm=j-1
        jp=j+1
             do i=2,imaxm
                if (rmask(i,j).eq.1.0)then
             im=i-1
             ip=i+1
             zetun(i,j)=
           +  (un(im,j,km)+un(ip,j,km)-2.*un(i,j,km))*recdx2
           +  + ((un(i,jp,km)-un(i,j,km))-
           +  (un(i,j,km)-un(i,jm,km)))*recdy2

             zetvn(i,j)=
           +  ((vn(ip,j,km)-vn(i,j,km))-
           +  (vn(i,j,km)-vn(im,j,km)))*recdx2
           +  + (vn(i,jp,km)+vn(i,jm,km)-2.*vn(i,j,km))*recdy2
              endif

           end do

    end do
c$omp end do
c$omp end parallel

Upvotes: 1

Views: 263

Answers (1)

Vladimir F Героям слава
Vladimir F Героям слава

Reputation: 60008

The code is not valid. jm, jp, im and ip have to be private at least. Also, why you require ordered? It definitely slows it down. Also, hhy schedule dynamic with such a large chunk? Just use static.

Also, use some line indentation when coding, or at least when presenting your code to others.

Upvotes: 2

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