/*
 *  mpich7.c
 *  $Id$
 *
 *  Copyright (C) 2007 Andrew Smirnoff
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <string.h>

#include "mpi.h"

int main(int argc, char* argv[])
{
     int myrank;
     int **a, **b;
     int *veca, *vecb;
     int *buf;
     int i,j,k;
     int n;
     int next;
     int prev;
     int min = 2147483647;
     int res;
     
     MPI_Status status;
     
     MPI_Init(&argc,&argv);
     MPI_Comm_rank(MPI_COMM_WORLD,&myrank);
     MPI_Comm_size(MPI_COMM_WORLD,&n);

     veca = (int *) malloc(sizeof(int) * n);
     buf = (int *) malloc(sizeof(int) * n);
     vecb = (int *) malloc(sizeof(int) * n);
     
     if (myrank == 0)
     {
	  a = (int **) malloc(sizeof(int *) * n);
	  b = (int **) malloc(sizeof(int *) * n);

	  srand(time(0));
	  
	  for (i = 0; i < n; i++)
	  {
	       a[i] = (int *) malloc(sizeof(int) * n);
	       b[i] = (int *) malloc(sizeof(int) * n);
	       for (j = 0; j < n; j++)
	       {
		    a[i][j] = rand() % 10;
		    b[i][j] = rand() % 10;
	       }
	  }
	  
	  printf("a = \n");
	  for (i = 0; i < n; i++)
	  {
	       for (j = 0; j < n; j++)
		    printf("%2d ", a[i][j]);
	       printf("\n");
	  }

	  printf("b = \n");
	  for (i = 0; i < n; i++)
	  {
	       for (j = 0; j < n; j++)
		    printf("%2d ", b[i][j]);
	       printf("\n");
	  }
	  printf("Sending to processes...\n");
	  fflush(stdout);

	  for (i = 1; i < n; i++)
	  {
	       for (j = 0; j < n; j++)
	       {
		    veca[j] = a[i][j];
		    vecb[j] = b[j][i];
	       }
	       MPI_Send(veca, n, MPI_INT, i, 0, MPI_COMM_WORLD);
	       MPI_Send(vecb, n, MPI_INT, i, 0, MPI_COMM_WORLD);
	  }

	  printf("Sended!\n");
	  fflush(stdout);

	  for (j = 0; j < n; j++)
	  {
	       veca[j] = a[0][j];
	       vecb[j] = b[j][0];
	  }

     }
     else
     {
	  MPI_Recv(veca, 2 * n, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
	  MPI_Recv(vecb, 2 * n, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
     }

     next = myrank + 1;
     prev = myrank - 1;
     if (myrank == 0) prev = n - 1;
     if (myrank == n-1) next = 0;

     for (i = 0; i < n; i++)
     {
	  res = 0;
	  for (j = 0; j < n; j++)
	       res += veca[j] * vecb[j] * j;
	  
	  if (res < min)
	       min = res;

	  if (i < n)
	  {
	       MPI_Sendrecv (vecb, n, MPI_INT, next, 0, buf, n, MPI_INT, prev, 0, MPI_COMM_WORLD, &status);
	       for (j = 0; j < n; j++)
	            vecb[j] = buf[j];
	  }
     }

     if (myrank != 0)
	  MPI_Send(&min, 1, MPI_INT, 0, 0, MPI_COMM_WORLD);
     else
     {
	  veca[0] = min;
	  for (i = 1; i < n; i++)
	       MPI_Recv(&(veca[i]), 1, MPI_INT, i, 0, MPI_COMM_WORLD, &status);

	  printf("Result:  ");
	  for (i = 0; i < n; i++)
	       printf("%d ", veca[i]);
	  printf("\n");

     }

     MPI_Finalize();
     
     free(veca);
     free(buf);
}