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Subject: Re: [OMPI users] Issue with Profiling Fortran code
From: Anthony Chan (chan_at_[hidden])
Date: 2008-12-05 19:07:12


Hi George,

----- "George Bosilca" <bosilca_at_[hidden]> wrote:

> 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).

Yes, you are right. I was being sloppy (it was late, so just cut/paste
from Nick's code), the correct code should be

void mpi_comm_rank_(MPI_Fint *comm, MPI_Fint *rank, MPI_Fint *info) {
   printf("mpi_comm_rank call successfully intercepted\n");
    *info = PMPI_Comm_rank(MPI_Comm_f2c(*comm),*rank);
}

A.Chan
>
> 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" <nwright_at_[hidden]> 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
> >>
> >>
> >>
> >> _______________________________________________
> >> users mailing list
> >> users_at_[hidden]
> >> http://www.open-mpi.org/mailman/listinfo.cgi/users
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
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