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

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 wrote:

On Sep 15, 2009, at 8:12 PM, alfC wrote:

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I am using MPI in combination with BLACS and apparently it works with MPI_Init but not with boost.MPI

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when I use

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#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<

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the program output (correctly): "0 1"

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But when I use

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   boost::mpi::environment env(argc, argv); //instead of MPI_Init(argc, argv);

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the programs outputs (incorrectly):  "0 -1".

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The point being that apparently boost::mpi::environment is not equivalent to MPI_Init/MPI_Finalize.

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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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