/*  cpi_log.c  10 February 2000  */

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

/******************************************************************************/

double f ( double a )

/******************************************************************************/

{
    return (4.0 / (1.0 + a*a));
}
/******************************************************************************/

int main ( int argc, char *argv[] )

/******************************************************************************/
{
  double a;
  int done = 0;
  double endwtime;
  double h;
  int i;
  int myid;
  double mypi;
  int n;
  int numprocs;
  double pi;
  double PI25DT = 3.141592653589793238462643;
  int rc;
  int repeat;
  double startwtime;
  double sum;
  double x;

  MPI_Init ( &argc, &argv );
  MPI_Comm_size ( MPI_COMM_WORLD, &numprocs );
  MPI_Comm_rank ( MPI_COMM_WORLD, &myid );

  MPE_Init_log();

  if (myid == 0) {
    MPE_Describe_state(1, 2, "Broadcast", "red:vlines3");
    MPE_Describe_state(3, 4, "Compute",   "blue:gray3");
    MPE_Describe_state(5, 6, "Reduce",    "green:light_gray");
    MPE_Describe_state(7, 8, "Sync",      "yellow:gray");
  }

  while (!done) {
    if (myid == 0) {
      printf("Enter the number of intervals: (0 quits) ");
      scanf("%d",&n);
      startwtime = MPI_Wtime();
    }
    MPI_Barrier(MPI_COMM_WORLD);
    MPE_Start_log();

    MPE_Log_event(1, 0, "start broadcast");
    MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
    MPE_Log_event(2, 0, "end broadcast");
    
    if (n == 0) {

      done = 1;

    } else {

      for (repeat=5; repeat; repeat--) {

        MPE_Log_event(7,0,"Start Sync");
        MPI_Barrier(MPI_COMM_WORLD);
        MPE_Log_event(8,0,"End Sync");
        MPE_Log_event(3, 0, "start compute");

        h   = 1.0 / (double) n;
        sum = 0.0;
        for (i = myid + 1; i <= n; i += numprocs) {
          x = h * ((double)i - 0.5);
          sum = sum + f(x);
        }

        mypi = h * sum;
        MPE_Log_event(4, 0, "end compute");
        fprintf( stderr, "[%d] mypi = %lf\n", myid, mypi );

        MPE_Log_event(5, 0, "start reduce");
        MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
        MPE_Log_event(6, 0, "end reduce");

        if (myid == 0) {
          printf("pi is approximately %.16f, Error is %.16f\n",
            pi, fabs(pi - PI25DT));
          endwtime = MPE_Wtime();
          printf("wall clock time = %f\n", endwtime-startwtime);         
        }

      }

    }
    MPE_Stop_log();
  }
/*
  fprintf(stderr,"about to finish_log\n");
*/
  MPE_Finish_log("cpi_log.log");
/*
  fprintf(stderr,"through finish_log, about to finalize\n");
*/
  MPI_Finalize();
/*
  fprintf(stderr,"through finalize\n");
*/
}