。。。
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <mpi.h>
double f(double x) {
? ? return 4.0 / (1.0 + x * x);
}
int main(int argc, char **argv) {
? ? int rank, size, i, n;
? ? double pi, h, sum, x;
? ? MPI_Init(&argc, &argv);
? ? MPI_Comm_rank(MPI_COMM_WORLD, &rank);
? ? MPI_Comm_size(MPI_COMM_WORLD, &size);
? ? if (argc != 2) {
? ? ? ? if (rank == 0) {
? ? ? ? ? ? printf("Usage: mpiexec -n <num_procs> %s <num_steps>\n", argv[0]);
? ? ? ? }
? ? ? ? MPI_Finalize();
? ? ? ? return 1;
? ? } else {
? ? ? ? n = atoi(argv[1]);
? ? }
? ? // 梯形積分法
? ? double start_time_trap = MPI_Wtime();? // 記錄開始時間
? ? h = 1.0 / n;
? ? int chunk = n / size;
? ? int start = rank * chunk;
? ? int end = (rank == size - 1) ? n : (rank + 1) * chunk;
? ? sum = 0.0;
? ? for (i = start; i < end; i++) {
? ? ? ? x = h * (i + 0.5);
? ? ? ? sum += f(x);
? ? }
? ? sum *= h;
? ? MPI_Reduce(&sum, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD); // 結(jié)果匯總
? ? if (rank == 0) {
? ? ? ? double end_time_trap = MPI_Wtime();? // 記錄結(jié)束時間
? ? ? ? printf("Using trapezoidal rule with %d processes, %d steps, pi = %.16f, time = %f s\n", size, n, pi, end_time_trap - start_time_trap);
? ? }
? ? // 蒙特卡洛法
? ? int total_samples = atoi(argv[1]) / size;
? ? double start_time_monte = MPI_Wtime();? // 記錄開始時間
? ? srand(time(NULL) + rank * 1000);
? ? count = 0;
? ? for (i = 0; i < total_samples; i++) {
? ? ? ? x = (double)rand() / RAND_MAX;
? ? ? ? y = (double)rand() / RAND_MAX;
? ? ? ? if (x * x + y * y <= 1.0) {
? ? ? ? ? ? count++;
? ? ? ? }
? ? }
? ? int global_count;
? ? MPI_Reduce(&count, &global_count, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);? // 結(jié)果匯總
? ? if (rank == 0) {
? ? ? ? double end_time_monte = MPI_Wtime();? // 記錄結(jié)束時間
? ? ? ? pi = 4.0 * (double)global_count / (double)atoi(argv[1]);
? ? ? ? printf("Using Monte Carlo method with %d processes, %d samples, pi = %.16f, time = %f s\n", size, atoi(argv[1]), pi, end_time_monte - start_time_monte);
? ? }
? ? MPI_Finalize();
? ? return 0;
}
