Re: [OMPI users] Issue with Profiling Fortran code

[George Bosilca]

On Dec 5, 2008, at 03:16 , Anthony Chan wrote:

void mpi_comm_rank_(MPI_Comm *comm, int *rank, int *info) {
   printf("mpi_comm_rank call successfully intercepted\n");
   *info = PMPI_Comm_rank(comm,rank);
}

Unfortunately this example is not correct. The real Fortran prototype  
for the MPI_Comm_rank function is
void mpi_comm_rank_(MPI_Fint *comm, MPI_Fint *rank, MPI_Fint *ierr).

As you might notice there is no MPI_Comm (and believe me for Open MPI  
MPI_Comm is different than MPI_Fint), and there is no guarantee that  
the C int is the same as the Fortran int (looks weird but true).  
Therefore, several conversions are required in order to be able to go  
from the Fortran layer into the C one.

As a result, a tool should never cross the language boundary by  
itself. Instead it should call the pmpi function as provided by the  
MPI library. This doesn't really fix the issue that started this email  
thread, but at least clarify it a little bit.

  george.


A.Chan

----- "Nick Wright" <nwri...@sdsc.edu> wrote:

Hi

I am trying to use the PMPI interface with OPENMPI to profile a
fortran
program.

I have tried with 1.28 and 1.3rc1 with --enable-mpi-profile switched
on.

The problem seems to be that if one eg. intercepts to call to
mpi_comm_rank_ (the fortran hook) then calls pmpi_comm_rank_ this  
then

calls MPI_Comm_rank (the C hook) not PMPI_Comm_rank as it should.

So if one wants to create a library that can profile C and Fortran
codes
at the same time one ends up intercepting the mpi call twice. Which  
is

not desirable and not what should happen (and indeed doesn't happen  
in

other MPI implementations).

A simple example to illustrate is below. If somebody knows of a fix  
to

avoid this issue that would be great !

Thanks

Nick.

pmpi_test.c: mpicc pmpi_test.c -c

#include<stdio.h>
#include "mpi.h"
void mpi_comm_rank_(MPI_Comm *comm, int *rank, int *info) {
  printf("mpi_comm_rank call successfully intercepted\n");
  pmpi_comm_rank_(comm,rank,info);
}
int MPI_Comm_rank(MPI_Comm comm, int *rank) {
  printf("MPI_comm_rank call successfully intercepted\n");
  PMPI_Comm_rank(comm,rank);
}

hello_mpi.f: mpif77 hello_mpi.f pmpi_test.o

      program hello
       implicit none
       include 'mpif.h'
       integer ierr
       integer myid,nprocs
       character*24 fdate,host
       call MPI_Init( ierr )
      myid=0
      call mpi_comm_rank(MPI_COMM_WORLD, myid, ierr )
      call mpi_comm_size(MPI_COMM_WORLD , nprocs, ierr )
      call getenv('HOST',host)
      write (*,*) 'Hello World from proc',myid,' out of',nprocs,host
      call mpi_finalize(ierr)
      end



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