Using send and receive Calls

• Example:

• rules of use:

  • mpi_send/recv are defined as blocking calls
    • the program should not assume blocking behaviour (small messages are buffered)
    • when these calls return, the buffers can be (re-)used
  • the arrival order of messages send from A and B to C is not determined. Two messages from A to B will arrive in the order sent.
  • Message Passing programming models are non-deterministic.

If(mod(myid,2).eq.0) then

idst = mod(id+1,np)

itag = 0

call mpi_send(A,N,MPI_REAL,idst,itag,MPI_COMM_WORLD,ierr)

if(ierr.ne.MPI_SUCCESS) print *,’error from’,id,np,ierr

else

isrc = mod(id-1+np,np)

itag = MPI_ANY_TAG

call mpi_recv(B,NSIZE,MPI_REAL,isrc,itag,MPI_COMM_WORLD,stat,ierr)

if(ierr.ne.MPI_SUCCESS) print *,’error from’,id,np,ierr

call mpi_get_count(stat,MPI_REAL,N)

endif

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