/*
This program demonstrate the use of MPI_Type_contiguous. 
Create a data type representing a row of an array and distribute a different row to all 
processes.
*/
/* Compile : mpicc -o type_contiguous type_contiguous.c */
/* Run     : mpirun -np 4 type_contiguous      */

#include "mpi.h"
#include <stdio.h>
#define SIZE 4

int main(int argc,char *argv[])  {
    int pid, np, source=0, dest, tag=1, i;
    double a[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};
    double b[SIZE];

MPI_Status stat;
MPI_Datatype rowtype;

MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD, &pid);
MPI_Comm_size(MPI_COMM_WORLD, &np);

MPI_Type_contiguous(SIZE, MPI_DOUBLE, &rowtype);
MPI_Type_commit(&rowtype);

if (np == SIZE) {
  if (pid == 0) {
     for (i=0; i<np; i++)
       MPI_Send(&a[i][0], 1, rowtype, i, tag, MPI_COMM_WORLD);
     }

  MPI_Recv(b, SIZE, MPI_DOUBLE, source, tag, MPI_COMM_WORLD, &stat);
  printf("rank= %d  b= %3.1f %3.1f %3.1f %3.1f\n",
         pid,b[0],b[1],b[2],b[3]);
  }
else
  printf("Must specify %d processors. Terminating.\n",SIZE);

MPI_Finalize();
}