// ==================================================================
// Author: Jean-Michel Richer
// Email: jean-michel.richer@univ-angers.fr
// Date: Aug 2016
// Purpose: Demonstrate basic functionnalities of MPI with C
// ==================================================================
#include <iostream>
#include <cstdlib>
#include <unistd.h> // for sleep
using namespace std;
#include <mpi.h>

// ==============================================================
// C version 
// ==============================================================

int main(int argc, char ** argv) {
	// maximum number of CPUs
	int max_cpus;
	// cpu identifier (called rank)
	int cpu_rank;
	// C-string to store the name of the host
	char cpu_name[MPI_MAX_PROCESSOR_NAME];
	// length of the C-string
	int length;


	// initialization also using command line parameters
	MPI_Init(&argc, &argv); 
	
	// get number of programs running
	MPI_Comm_size(MPI_COMM_WORLD, &max_cpus);

	// get program identifier
	MPI_Comm_rank(MPI_COMM_WORLD, &cpu_rank);

    // get cpu name 
	MPI_Get_processor_name(cpu_name, &length);

	sleep(cpu_rank);
	
	cerr << "running on " << cpu_name << " with id=" << cpu_rank << "/";
	cerr << max_cpus << endl;
    
    // free resources, don't forget !
	MPI_Finalize();

	exit(EXIT_SUCCESS);
}