#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <signal.h>
#include "mpi.h"
double f(double a){
return(4*sqrt(1-a*a));
}
//extern f(double a);
double mid_point_rule(double start, double delta_x){
return delta_x*f(start+(delta_x/2.)) ;
}
double rectangular_rule(double start, double delta_x){
return delta_x*f(start) ;
}
double simpsons_rule(double start, double delta_x){
return(delta_x/6.0)*(f(start)+4*f(start+(delta_x/2.))+f(start+delta_x)) ;
}
double (*rule)(double start, double delta_x);
int main(int argc,char *argv[],char *envp[]){
int done = 0, n, myid, numprocs, mpi_error,namelen,i_counter;
int buffer[2],local_intervals;
double local_start;
double PI_to_25dp = 3.141592653589793238462643;
double mypi, pi, delta_x;
double startwtime, endwtime,beginwtime;
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);
printf("Process number %d on processor %s \n", myid, processor_name, numprocs);
fflush(stdout);
n = 0;
if (myid == 0) {
buffer[0]=atoi(getenv("mpiMethod"));
buffer[1]=atoi(getenv("mpiCount"));
startwtime = MPI_Wtime();
}//end setup by the master process..0
MPI_Bcast(buffer, 2, MPI_INT, 0, MPI_COMM_WORLD);
if (buffer[0] == 0)
done = 1;
else {
n=buffer[1];
switch (buffer[0]) {
case 0:
done=1;
break;
case 1:
rule=&rectangular_rule;
break;
case 2:
rule=&mid_point_rule;
break;
case 3:
rule=&simpsons_rule;
break;
}
/*******set up this processes part of the calculation********/
delta_x = 1.0 / (double) n;
local_start=(1.0/numprocs)*(myid);
local_intervals=n/numprocs;
/******* The next statments are just for diagnostics ********/
//printf("process=%d local start = %.16f local intervals = %d\n",myid,local_start,local_intervals);
//fflush(stdout);
/**********************************************************/
mypi=0.0;
i_counter=0;
for (i_counter=0;i_counter<local_intervals;i_counter++)
mypi+=( *rule)(local_start+i_counter*delta_x,delta_x);
/* The next statment---either sends mypi back to 0 or if 0 does the calculation*/
MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
if (myid == 0) {
printf("\npi is approximately %.16f, Relative Error is %16.8e\n",
pi, (double)100 * (pi - PI_to_25dp)/PI_to_25dp);
fflush(stdout);
endwtime = MPI_Wtime();
printf("wall clock time = %f\n", endwtime-startwtime);
fflush(stdout);
}
}
mpi_error=MPI_Finalize();
if (MPI_SUCCESS!=mpi_error)
return mpi_error;
else
return 0;
}