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/*
* $Id: cpi++.C,v 1.2 1996/03/08 21:02:41 gropp Exp $
*/
#include <mpi++.h>
#include <stdio.h>
#include <math.h>
double f(double a)
{
return (4.0 / (1.0 + a*a));
}
int main(int argc, char *argv[])
{
int done = 0, n, myid, numprocs, i, rc;
double PI25DT = 3.141592653589793238462643;
double mypi, pi, h, sum, x, a;
double startwtime, endwtime;
MPI_COMM_WORLD.Init (argc, argv);
MPI_COMM_WORLD.Rank (myid) ;
MPI_COMM_WORLD.Size (numprocs) ;
while (!done)
{
if (myid == 0)
{
printf("Enter the number of intervals: (0 quits) ");
scanf("%d",&n);
startwtime = MPI_Wtime();
}
MPI_COMM_WORLD.Bcast(&n, 1, MPI_INT, 0);
if (n == 0)
done = 1;
else
{
h = 1.0 / (double) n;
sum = 0.0;
for (i = myid + 1; i <= n; i += numprocs)
{
x = h * ((double)i - 0.5);
sum += f(x);
}
mypi = h * sum;
MPI_COMM_WORLD.Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0);
if (myid == 0)
{
printf("pi is approximately %.16f, Error is %.16f\n",
pi, fabs(pi - PI25DT));
endwtime = MPI_Wtime();
printf("wall clock time = %f\n",
endwtime-startwtime);
}
}
}
MPI_COMM_WORLD.Finalize();
return (MPI_SUCCESS);
}
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