openmpi编程的计算π的程序Ubuntu

下面是使用OpenMPI编写的计算π的程序示例，运行于Ubuntu系统上：

#include <stdio.h>
#include <mpi.h>

int main(int argc, char *argv[])
{
    int rank, size, i, n, tag = 0;
    double PI25DT = 3.141592653589793238462643;
    double mypi, pi, h, sum, x;
    MPI_Status status;
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    while (1)
    {
        if (rank == 0)
        {
            printf("Enter the number of intervals: (0 quits) ");
            scanf("%d", &n);
        }
        MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
        if (n == 0)
            break;
        else
        {
            h = 1.0 / (double)n;
            sum = 0.0;
            for (i = rank + 1; i <= n; i += size)
            {
                x = h * ((double)i - 0.5);
                sum += (4.0 / (1.0 + x * x));
            }
            mypi = h * sum;
            MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
            if (rank == 0)
            {
                printf("pi is approximately %.16f, Error is %.16f\n",
                       pi, fabs(pi - PI25DT));
            }
        }
    }
    MPI_Finalize();
    return 0;
}

编译命令：

mpicc -o mpi_pi mpi_pi.c

运行命令：

mpirun -np 4 mpi_pi

其中，`-np`参数指定进程数量，可以根据需要进行调整。