L10Ex4.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mpi.h>

int main(int argc, char **argv) {
	int rank, size, namelen, version, subversion, universe_size;
	int globalrank, sumrank;
	MPI_Comm family_comm, allcomm;
	char processor_name[MPI_MAX_PROCESSOR_NAME], worker_program[100];
	int rank_from_child, ich;
	MPI_Status status;
	MPI_Info hostinfo;
	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	MPI_Comm_size(MPI_COMM_WORLD, &size);
	MPI_Get_processor_name(processor_name, &namelen);
	MPI_Get_version(&version, &subversion);
	printf("I'm manager %d of %d on %s running MPI %d.%d\n", rank, size, processor_name, version, subversion);
	if (size != 1) printf("Error: Only one manager process should be running, but %d were started.\n", size);
	universe_size = 4;
	MPI_Info_create(&hostinfo);
	MPI_Info_set(hostinfo, "host", "compute-0-0,compute-0-3");
	printf("Spawning %d worker processes\n", universe_size - 1);
	MPI_Comm_spawn("./L10Ex4_child.exe", MPI_ARGV_NULL, universe_size - 1, hostinfo, 0, MPI_COMM_SELF, &family_comm, MPI_ERRCODES_IGNORE);
	MPI_Intercomm_merge(family_comm, 1, &allcomm);
	MPI_Comm_rank(allcomm, &globalrank);
	printf("manager: global rank is %d,rank is %d \n", globalrank, rank);

	//MPI_Allreduce(&globalrank, &sumrank, 1, MPI_INT, MPI_SUM, allcomm);
	MPI_Reduce(&globalrank, &sumrank, 1, MPI_INT, MPI_SUM, 0, allcomm);
	MPI_Bcast(&sumrank, 1, MPI_INT, 0, allcomm);

	printf("sumrank (root) after  allreduce  on  process  %d  is  %d  \n", rank, sumrank);
	MPI_Comm_disconnect(&family_comm);
	MPI_Finalize();
	return 0;
}