Linux MPI集群配置

MPI是一种并行计算架构，MPICH是MPI的一种实现，本集群使用虚拟机安装，操作系统是ubuntu14.04，使用三台机器，用户名都是ubuntu，机器名分别是ub0, ub1, ub2

安装MPICH

下载：http://www.mpich.org/static/downloads/3.0.4/mpich-3.0.4.tar.gz
源码安装

$ tar -xzvf soft/mpich-3.0.4.tar.gz
$ cd mpich-3.0.4/
$ ./configure --prefix=/usr/local/mpich
$ make && sudo make install

安装后加入环境变量到/etc/profile文件，并执行 source /etc/profile，追加内容到/etc/profile

PATH=$PATH:/usr/local/mpich/bin
MANPATH=$MANPATH:/usr/local/mpich/man
export PATH MANPATH

单节点测试

复制源代码包下的examples目录到安装目录下

cp -r examples/ /usr/local/mpich

执行

mpirun -np 10 ./examples/cpi

输出结果如下：

Process 0 of 10 is on ub0
Process 9 of 10 is on ub0
Process 1 of 10 is on ub0
Process 4 of 10 is on ub0
Process 5 of 10 is on ub0
Process 7 of 10 is on ub0
Process 2 of 10 is on ub0
Process 3 of 10 is on ub0
Process 6 of 10 is on ub0
Process 8 of 10 is on ub0

pi is approximately 3.1415926544231256, Error is 0.0000000008333325
wall clock time = 0.020644

集群配置
- 需要先配置ssh免密码登录，把ub0(机器名)当作master node，也即主节点，其他是slave node，也即从节点。配置免密码ssh登录的步骤
  - 你需要把主节点的公钥分别发送给从节点，这样主节点登录从节点才是可信任的，就不用密码，以配置ub0的公钥给ub1为例
  - ub0产生公钥
  - ```
  $ ssh-keygen -t rsa
```
  一路enter就行了
- 把ub0的/home/ubuntu/.ssh/id_rsa.pub 发送到ub1的/home/ubuntu/.ssh/下，如果没有/home/ubuntu/.ssh/就mkdir .ssh
- 在ub1的/home/ubuntu/.ssh/下执行
- ```
$ cat id_rsa.pub >> authorized_keys
```
  - 尝试ub0 ssh到ub1试试，看看是否成功设置无密码登录，如果成功，就继续下一个节点吧
- 复制编译程序到其他机器上面，这样就不用在其他机器上进行源码编译mpich，节省了时间
1. ```
scp -r mpich ub1:/usr/local/
scp -r mpich ub2:/usr/local/
```
- 在ub0, ub1, ub2的/etc/hosts上追加
- ```
192.168.0.2 ub0
192.168.0.3 ub1
192.168.0.4 ub2
```
  注意，三台机器的/etc/hosts都要追加
- 把主节点的/usr/local/mpich/example/cpi这个计算圆周率的可执行文件复制到/home/ubuntu目录下，并且发送到ub1和ub2的/home/ubuntu目录
- 在主节点的/home/ubuntu目录下增加servers文件，记录集群的机器名和对应的进程数
- ```
ub0:2
ub1:2
ub2:2
```
- 在ub0的/home/ubuntu目录下执行
- ```
$ mpiexec -n 10 -f servers ./cpi
```
  你就可以看到下面的结果
- ```
Process 0 of 10 is on ub0
Process 1 of 10 is on ub1
Process 4 of 10 is on ub0
Process 5 of 10 is on ub2
Process 6 of 10 is on ub1
Process 7 of 10 is on ub2
Process 8 of 10 is on ub0
Process 9 of 10 is on ub1
Process 2 of 10 is on ub2
Process 3 of 10 is on ub1
pi is approximately 3.1415926544231256, Error is 0.0000000008333325
wall clock time = 0.018768
```