Re: [Boost-users] [mpi] enviroment constructor different from MPI_Init

Subject: Re: [Boost-users] [mpi] enviroment constructor different from MPI_Init
From: AlfC (alfredo.correa_at_[hidden])
Date: 2009-09-15 17:45:26

ok I tried your code and MPI_Init-like version still works and
boost::mpi::environment version doesn't (i.e. Blacs returns the wrong
nprocs)

In fact the Blacs_pinfo returns just the same as if I don't define
anything so effectivelly the boost::mpi::environment is doing nothing.

I even checked that boost::mpi::environment::initialized() is false
before constructing boost::mpi::environment and true after, but still
Blacs_pinfo reports as if MPI is not initialized.

On Sep 15, 11:55 am, Matthias Troyer <tro..._at_[hidden]> wrote:
> On Sep 15, 2009, at 8:12 PM, alfC wrote:
>
>
>
>
>
> > I am using MPI in combination with BLACS and apparently it works with
> > MPI_Init but not with boost.MPI
>
> > when I use
>
> > #include "blacs.h"
> > int main(int argc, char* argv[]) {
> >    MPI_Init(&argc,&argv);
> >    int nprocs=0;
> >    int mype=0;
> >    Cblacs_pinfo( &mype, &nprocs ); // overwrites the pointee, that is
> > how Cblacs_pinfo works
> >    std::cout<<mype<<" "<<nprocs<<std::endl;
>
> > the program output (correctly): "0 1"
>
> > But when I use
>
> >    boost::mpi::environment env(argc, argv); //instead of MPI_Init(argc,
> > argv);
>
> > the programs outputs (incorrectly):  "0 -1".
>
> > The point being that apparently boost::mpi::environment is not
> > equivalent to MPI_Init/MPI_Finalize.
>
> > Any idea of what is difference between MPI_Init and
> > boost::mpi::environment?
>
> The constructor is equivalent to the following:
>
>    int flag;
>    MPI_Initialized(&flag);
>    if (!(flag!=0))
>      MPI_Init(&argc, &argv);
>    MPI_Errhandler_set(MPI_COMM_WORLD, MPI_ERRORS_RETURN);
>
> Matthias Troyer
>
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