source: CIVL/examples/mpi/routines/Gather_Scatter/mpi_scatter.c

/******************************************************************************
* FILE: mpi_scatter.c
* DESCRIPTION:
*   MPI tutorial example code: Collective Communications
* AUTHOR: Blaise Barney
* LAST REVISED: 04/13/05
******************************************************************************/
#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#define SIZE 4

int main (int argc, char *argv[])
{
int numtasks, rank, sendcount, recvcount, source;
float sendbuf[SIZE * SIZE] = {
  1.0, 2.0, 3.0, 4.0,
  5.0, 6.0, 7.0, 8.0,
  9.0, 10.0, 11.0, 12.0,
  13.0, 14.0, 15.0, 16.0};
float recvbuf[SIZE];

MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &numtasks);

if (numtasks == SIZE) {
  source = 1;
  sendcount = SIZE;
  recvcount = SIZE;
  MPI_Scatter(sendbuf,sendcount,MPI_FLOAT,recvbuf,recvcount,
             MPI_FLOAT,source,MPI_COMM_WORLD);

  printf("rank= %d  Results: %f %f %f %f\n",rank,recvbuf[0],
         recvbuf[1],recvbuf[2],recvbuf[3]);
  //add assertions
  for(int i=0; i<SIZE; i++)
    assert(recvbuf[i] == *(sendbuf + SIZE * rank + i));
 }
else
  printf("Must specify %d processors. Terminating.\n",SIZE);

MPI_Finalize();
}