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

int main( int argc, char *argv[]) {
  int myrank, size, left, right;
  double start_time, time, max_time;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank( MPI_COMM_WORLD, &myrank );
  MPI_Comm_size( MPI_COMM_WORLD, &size );
  MPI_Request request[2];
  
  left  = myrank == 0      ? size-1 : myrank-1;
  right = myrank == size-1 ?      0 : myrank+1;
  
  printf("%d > %d > %d\n", left, myrank, right);

  int BUFSIZE = atoi(argv[1]);
  int i, j;
  double comp[BUFSIZE];
  double arr[BUFSIZE];
  double recv[BUFSIZE];
  
  for ( i=0; i < size; i++ ) {
    arr[i]  = 1.0*myrank+i;
    comp[i] = 1.0*myrank+i;
  }

  start_time = MPI_Wtime();
  MPI_Isend(arr,  BUFSIZE, MPI_DOUBLE, right, 1, MPI_COMM_WORLD, &request[0]);
  MPI_Irecv(recv, BUFSIZE, MPI_DOUBLE, left,  1, MPI_COMM_WORLD, &request[1]);
 
  for ( j=0; j < 10000; j++ ) {
    for ( i=0; i < size; i++ ) {
      comp[i] = 3.14*cos(myrank+i) + tan(arr[i]/2.0);
      comp[i] = log(pow(comp[i],4));
    }
  }
  
  MPI_Waitall(2, request, MPI_STATUSES_IGNORE);
  time = MPI_Wtime () - start_time;

  MPI_Reduce (&time, &max_time, 1, MPI_DOUBLE, MPI_MAX, size-1, MPI_COMM_WORLD);
  if (myrank == size-1) printf ("%lf\n", max_time);

  MPI_Finalize();
  return 0;
}