OK, here's my MPIDawmMPIC.c file:
/*
============================================================================
Name : MPIDawmMPIC.c
Author : Krime
Version :
Copyright : SYSU Parallel
Description : Calculate Pi in MPI
============================================================================
*/
#include <mpi.h>
#include <stdio.h>
#include <string.h>
void
calc_pi(int rank, int num_procs)
{
int i;
int num_intervals;
double h;
double mypi;
double pi;
double sum;
double x;
/* set number of intervals to calculate */
if (rank == 0) {
num_intervals = 100000000;
}
/* tell other tasks how many intervals */
MPI_Bcast(&num_intervals, 1, MPI_INT, 0, MPI_COMM_WORLD);
/* now everyone does their calculation */
h = 1.0 / (double) num_intervals;
sum = 0.0;
for (i = rank + 1; i <= num_intervals; i += num_procs) {
x = h * ((double)i - 0.5);
sum += (4.0 / (1.0 + x*x));
}
mypi = h * sum;
/* combine everyone's calculations */
MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
if (rank == 0) {
printf("PI is approximately %.16f\n", pi);
}
}
int
main(int argc, char *argv[])
{
int my_rank; /* rank of process */
int num_procs; /* number of processes */
int source; /* rank of sender */
int dest = 0; /* rank of receiver */
int tag = 0; /* tag for messages */
char message[100]; /* storage for message */
MPI_Status status ; /* return status for receive */
/* start up MPI */
MPI_Init(&argc, &argv);
/* find out process rank */
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
/* find out number of processes */
MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
if (my_rank != 0) {
/* create message */
sprintf(message, "Greetings from process %d!", my_rank);
/* use strlen+1 so that '\0' get transmitted */
MPI_Send(message, strlen(message)+1, MPI_CHAR,
dest, tag, MPI_COMM_WORLD);
} else {
printf("Num processes: %d\n",num_procs);
for (source = 1; source < num_procs; source++) {
MPI_Recv(message, 100, MPI_CHAR, source, tag,
MPI_COMM_WORLD, &status);
printf("Process 0 received \"%s\"\n",message);
}
/* now return the compliment */
sprintf(message, "Hi, how are you?");
}
MPI_Bcast(message, strlen(message)+1, MPI_CHAR, dest, MPI_COMM_WORLD);
if (my_rank != 0) {
printf("Process %d received \"%s\"\n", my_rank, message);
}
/* calculate PI */
calc_pi(my_rank, num_procs);
/* shut down MPI */
MPI_Finalize();
return 0;
}
