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

#include "mpi.h"

double **alloc2d( int m, int n ) {
  double **A;
  int i;
  A = (double **)malloc(m*sizeof(double *));
  A[0] = (double *)malloc(m*n*sizeof(double));
  for ( i=1; i<m; i++ )
    A[i] = A[0] + i*n;
  return A;
}




int main(int argc, char** argv) {
  int i, j, me, np, N;
  double **A;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &me);
  MPI_Comm_size(MPI_COMM_WORLD, &np);
  N = np;
  int disp[N], count[N];
  double rbuf[me+1];
  if ( me==0 ) {
    A = alloc2d(N,N);
    for ( i=0; i<N; i++ )
      for ( j=0; j<N; j++ )
	A[i][j] = 10*(i+1) + j + 1;    
  } else
    A = alloc2d(1,1);  // dummy array (placeholder)
  
  for ( i=0; i<N; i++ ) {
    disp[i] = i*N;      // starting position and lengths of 
    count[i] = i+1;     // lower triangle portion of rows
  }

  MPI_Scatterv( &A[0][0], count, disp, MPI_DOUBLE, 
		    rbuf, me+1, MPI_DOUBLE, 0, MPI_COMM_WORLD ); 

  printf("P%d got values: ",me);
  for ( j=0; j<=me; j++ )
    printf("%lf ",rbuf[j]);
  printf("\n");

  MPI_Finalize();
  return 0;
}