Hi, all,

 

I am parallelizing a CFD 2D code in FORTRAN+OPENMPI. Suppose that the grid (all triangles) is partitioned among 8 processes using METIS. Each process has different number of neighboring processes. Suppose each process has n elements/faces whose data it needs to sends to corresponding neighboring processes, and it has m number of elements/faces on which it needs to get data from corresponding neighboring processes. Values of n and m are different for each process. Another aim is to hide the communication behind computation. For this I do the following for each process:

 

DO j = 1 to n

CALL MPI_ISEND (send_data, num, type, dest(j), tag, MPI_COMM_WORLD, ireq(j), ierr)

ENDDO

 

DO k = 1 to m

CALL MPI_RECV(recv_data, num, type, source(k), tag, MPI_COMM_WORLD, status, ierr)

ENDDO

 

 This solves my problem. But it gives memory leakage; Ram gets filled after few thousands of iteration. What is the solution/remedy? How should I tackle this?

 

In another CFD code I removed this problem of memory-filling by following (in that code n=m) :

 

DO j = 1 to n

CALL MPI_ISEND (send_data, num, type, dest(j), tag, MPI_COMM_WORLD, ireq(j), ierr)

ENDDO

 

CALL MPI_WAITALL(n,ireq,status,ierr)

 

DO k = 1 to n

CALL MPI_RECV(recv_data, num, type, source(k), tag, MPI_COMM_WORLD, status, ierr)

ENDDO

 

But this is not working in current code; and the previous code was not giving correct results with large number of processes.

 

Please suggest solution.

 

THANKS A LOT FOR YOUR KIND ATTENTION.

 

With best regards,

Amjad Ali.