scatter and gather simple example in c

scatter_gather.cpp

#include "stdafx.h"
#include <iostream>
#include <time.h>

using namespace std;

#include "mpi.h"
#pragma comment(lib, "msmpi.lib")

void main(int argc, char *argv[])
{
	int myid, numprocs;
	
	MPI_Init(&argc, &argv);
	MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
	MPI_Comm_rank(MPI_COMM_WORLD, &myid);

	int *InputArr = new int[numprocs];

	if(myid == 0)
	{
		srand(time(NULL));
		for(int i = 0; i < numprocs; i++)
			InputArr[i] = rand() % 5;
	}

	int *rec = new int[1];
	MPI_Scatter(InputArr, 1, MPI_INT, rec, 1, MPI_INT, 0, MPI_COMM_WORLD);
	printf("num in process %d : %d", myid, *rec);

	int *gather = new int[1];
	MPI_Gather(&rec[0], 1, MPI_INT, &gather[0], 1, MPI_INT, 0, MPI_COMM_WORLD);
	if(myid == 0)
	{
		int my_sum = 0;
		for(int i = 0; i < numprocs; i++)
		{
			my_sum += *(gather+i);
		}
		printf("\n result : %d \n", my_sum);
	}
		
	MPI_Finalize();
}