It's my first time using Boost and is amazing. I'm trying to understand why this simple example bellow don't works as expected:

#include <iostream>

#include <boost/mpi.hpp>

using namespace std;

namespace mpi = boost::mpi;

int main ( int argc, char *argv[] )

{

mpi::environment env( argc, argv );

mpi::communicator world;

mpi::group subgroup( MPI_Group( world.group() ), true );

cout << "I'm process " << world.rank() << endl;

cout << "But in subgroup i'm process " << subgroup.rank() << endl;

cout << "And the subgroup size is... " << subgroup.size() << endl;

return 0;

} // ---------- end of function main ----------

1. Why every process has rank 1 in subgroup? I trying to figure out what happens, but without success.

The mpi::boost::group class has no copy constructor explicitly defined. That is true for many other classes in Boost.MPI...

2. It's safe to use the copy constructor generated by the compiler as follows?

mpi::group subgroup = world.group().exclude( discardedRanks.begin(), discardedRanks.end() );

Thanks in advance for any help.