/**********************************************************************
 * Derived datatypes in MPI/C
 *
 **********************************************************************/

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

int main(int argc, char *argv[]) {
  int rank, size,nx,ny,row,col,count,blocklen,stride;
  double *A;
  MPI_Status status;
  MPI_Datatype newtype;

  MPI_Init(&argc, &argv);               /* Initialize MPI               */
  MPI_Comm_size(MPI_COMM_WORLD, &size); /* Get the number of processors */
  MPI_Comm_rank(MPI_COMM_WORLD, &rank); /* Get my number                */
  
  nx=100; ny=150;
  A=(double *)malloc(nx*ny*sizeof(double));
  for (row=0; row<nx;row++)
    for (col=0; col<ny;col++)
      A[row*ny+col]=(double)col+1+(rank+1)*1000.0;

  count=nx; blocklen=1; stride=ny;
  MPI_Type_vector(count,blocklen,stride,MPI_DOUBLE,&newtype);
  MPI_Type_commit(&newtype);

  /* Send last column, notice the message length = 1 ! */
  if (rank == 0) {
    MPI_Send(&A[ny-1], 1, newtype, 1, 111, MPI_COMM_WORLD);

  } else if (rank==1) {
    MPI_Recv(&A[0], 1, newtype, 0, 111, MPI_COMM_WORLD, &status);
    for (row=0; row<nx; row++)
      printf("%f\n",A[row*ny]);
  }

  free(A);
  MPI_Type_free(&newtype);
  MPI_Finalize(); 

  return 0;
}