/*
 * MPI blocked 1D Jacobi
 * author: wimbo
 */

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

double f(int i, int n){
  if (i<n/2) return i;
  else return n-i-1;
}

/*
double f(int i, int n){
  return i;
}
*/


int main(int argc, char **argv) {
  int        id, p, i, j, k, n, t, m, v, vp;
  double     startwtime, endwtime;
  float      time;
  MPI_Status status;	/* return status for receive */
  double     *prev, *cur, *temp;
 
  MPI_Init( &argc, &argv );
  MPI_Comm_rank( MPI_COMM_WORLD, &id );
  MPI_Comm_size( MPI_COMM_WORLD, &p );
  if (argc < 4) {
    fprintf (stderr, "need problem size, #iterations and buffer size\n");
    goto EXIT;
  }
  if ((sscanf (argv[1], "%d", &n) < 1) ||  
      (sscanf (argv[2], "%d", &m) < 1) ||  
      (sscanf (argv[3], "%d", &k) < 1)) {  
    fprintf (stderr, "need int params\n");
    goto EXIT;
  }

  if (argc > 4) {
      v=1; 
      sscanf (argv[4], "%d", &vp); 
  } else v=0;  /* are we in verbose mode? vp = reporting process*/
 
  int block_size = (n/p+2*k);
  // Memory allocation for data array.
  prev  = (double *) malloc( sizeof(double) * block_size);
  cur   = (double *) malloc( sizeof(double) * block_size);

  if ( prev == NULL || cur == NULL ) {
     printf("[ERROR] : Failed to allocate memory.\n");
     goto EXIT;
  }

  t = 0;
  if(p==1){
     // Initialization
     startwtime = MPI_Wtime();
     for(i=0;i<n;i++)  prev[i] = f(i,n);
     cur[0] = f(0,n); cur[n-1] = f(n-1,n);
     while (t < m) {
      for ( i=1 ; i < n-1 ; i++ ) {
            cur[i] = (prev[i-1]+prev[i]+prev[i+1])/3;
       }
      temp = prev; prev = cur;  cur  = temp; t++;
      }
     if(v){
       for(i=0;i<n;i++) printf("%f ",prev[i]);
       printf("\n");
     }
     endwtime = MPI_Wtime();
     time = endwtime-startwtime;
     printf("Sequential process complete, time: %f\n", time);
     goto EXIT;     
   }
     

EXIT:
    MPI_Finalize();
    return 0;
}