ex4.cxx
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	// one shoule include mpi.h before stdio.h with recent versions of Intel compilers
	#include <mpi.h>

	#include <cstdlib> // for "getenv"
	#include <iostream>

	// A minimal MPI program
	// ---------------------

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

	// Each task owns its private set of the following variables
	// ---------------------------------------------------------

	int my_rank, tasks_number;
	char machine_name [512];
	int name_length;


	// We should start with...
	// -----------------------

	MPI_Init (& argc, & argv);


	// Getting information about the MPI environnement
	// -----------------------------------------------

	MPI_Comm_size (MPI_COMM_WORLD, & tasks_number);
	MPI_Comm_rank (MPI_COMM_WORLD, & my_rank);
	MPI_Get_processor_name (machine_name, & name_length);


	std::cout <<
	"Hello, my rank is " <<
	my_rank <<
	" among " <<
	tasks_number <<
	" tasks on machine " <<
	machine_name <<
	std::endl;
	std::cout.flush ();


	// Let's wait until all the tasks have reached this point
	// ------------------------------------------------------

	// MPI_Barrier (MPI_COMM_WORLD);

	if ( my_rank == 0 ) {
	std::cout <<
	"--- BARRIER! ---" <<
	std::endl;
	std::cout.flush ();
	}


	// ...and we should terminate by...
	// --------------------------------

	MPI_Finalize ();

	return 0;
	}