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Subject: Re: [OMPI users] Calling MPI_send MPI_recv from a fortran subroutine
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-02-28 11:07:39


On Feb 28, 2013, at 9:59 AM, Pradeep Jha <pradeep_at_[hidden]> wrote:

> Is it possible to call the MPI_send and MPI_recv commands inside a subroutine and not the main program?

Yes.

> I have written a minimal program for what I am trying to do. It is compiling fine but it is not working. The program just hangs in the "sendrecv" subroutine. Any ideas how can I do it?

You seem to have several errors in the sendrecv subroutine. I would strongly encourage you to use "implicit none" to avoid many of these errors. Here's a few errors I see offhand:

- tag is not initialized
- what's send_length(1)?
- use MPI_INTEGER, not MPI_INT (MPI_INT = C int, MPI_INTEGER = Fortran INTEGER)

> main.f
>
>
> program main
>
> include 'mpif.h'
>
> integer me, np, ierror
>
> call MPI_init( ierror )
> call MPI_comm_rank( mpi_comm_world, me, ierror )
> call MPI_comm_size( mpi_comm_world, np, ierror )
>
> call sendrecv(me, np)
>
> call mpi_finalize( ierror )
>
> stop
> end
>
> sendrecv.f
>
>
> subroutine sendrecv(me, np)
>
> include 'mpif.h'
>
> integer np, me, sender
> integer, dimension(mpi_status_size) :: status
>
> integer, dimension(1) :: recv, send
>
> if (me.eq.0) then
>
> do sender = 1, np-1
> call mpi_recv(recv, 1, mpi_int, sender, tag,
> & mpi_comm_world, status, ierror)
>
> end do
> end if
>
> if ((me.ge.1).and.(
> me.lt.np
> )) then
> send_length(1) = me*12
>
> call mpi_send(send, 1, mpi_int, 0, tag,
> & mpi_comm_world, ierror)
> end if
>
> return
> end
>
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-- 
Jeff Squyres
jsquyres_at_[hidden]
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