ubuntu安装配置mpich的步骤参考下面的博文：
https://blog.csdn.net/u010177634/article/details/53048371
本博文主要是解决安装mpich包之后测试程序时出现的问题。
按照网上的教程安装完成之后，使用以下命令来测试：
mpiexec -n <number> ./examples/cpi运行时需要自己修改<number>为自己的值，我指定的是<number>=4
在运行后出现了一下的问题，程序cpi所在的位置不允许运行。
/usr/bin/ld: cannot open output file /home/themingyi/Downloads/mpich-3.3/examples/.libs/14351-lt-cpi: Permission denied查找资料后发现是程序所在位置权限设置的问题；修改如下：
sudo chown -R "$USER:" /home/themingyi/Downloads/mpich-3.3/examples
chmod -R 777 /home/themingyi/Downloads/mpich-3.3/examples几点解释：
（1）The -R flag stands for recursive, so that directory and all its subfiles and subdirectories will change owner. Remove the -R flag to just change the permissions of the directory itself.
（2）运行时找到examples文件夹，就在自己下载的mpich包的解压文件中
运行结果如下：
cpi.c程序：
/* -*- Mode: C; c-basic-offset:5 ; indent-tabs-mode:nil ; -*- */↩
/*↩
* (C) 2001 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 ba ck */↩
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_WOR LD);↩
↩
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;↩
}↩