Pavan Balaji
b2e6fbd0ae
script generated to consistently point to the top-level copyright. Signed-off-by: Pavan Balaji <balaji@anl.gov>
61 linhas
1.5 KiB
C
61 linhas
1.5 KiB
C
/*
|
|
* Copyright (C) by Argonne National Laboratory
|
|
* See COPYRIGHT in top-level directory
|
|
*/
|
|
|
|
#include "mpi.h"
|
|
#include <stdio.h>
|
|
#include <math.h>
|
|
|
|
double f(double);
|
|
|
|
double f(double a)
|
|
{
|
|
return (4.0 / (1.0 + a * a));
|
|
}
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
int n, myid, numprocs, i;
|
|
double PI25DT = 3.141592653589793238462643;
|
|
double mypi, pi, h, sum, x;
|
|
double startwtime = 0.0, endwtime;
|
|
int namelen;
|
|
char processor_name[MPI_MAX_PROCESSOR_NAME];
|
|
|
|
MPI_Init(&argc, &argv);
|
|
MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
|
|
MPI_Comm_rank(MPI_COMM_WORLD, &myid);
|
|
MPI_Get_processor_name(processor_name, &namelen);
|
|
|
|
fprintf(stdout, "Process %d of %d is on %s\n", myid, numprocs, processor_name);
|
|
fflush(stdout);
|
|
|
|
n = 10000; /* default # of rectangles */
|
|
if (myid == 0)
|
|
startwtime = MPI_Wtime();
|
|
|
|
MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
|
|
|
|
h = 1.0 / (double) n;
|
|
sum = 0.0;
|
|
/* A slightly better approach starts from large i and works back */
|
|
for (i = myid + 1; i <= n; i += numprocs) {
|
|
x = h * ((double) i - 0.5);
|
|
sum += f(x);
|
|
}
|
|
mypi = h * sum;
|
|
|
|
MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
|
|
|
|
if (myid == 0) {
|
|
endwtime = MPI_Wtime();
|
|
printf("pi is approximately %.16f, Error is %.16f\n", pi, fabs(pi - PI25DT));
|
|
printf("wall clock time = %f\n", endwtime - startwtime);
|
|
fflush(stdout);
|
|
}
|
|
|
|
MPI_Finalize();
|
|
return 0;
|
|
}
|