Linux Java OpenMPI 安装

1. 下载jdk8:http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

2. 解压jdk:

   tar -zxvf /Dowloads/jdk-8u161-linux-x64.tar.gz
   

3. 下载openMPI：https://www.open-mpi.org/software/ompi/v3.0/

4. 解压OpenMPI：

   tar -zxvf /Dowloads/openmpi-3.0.0.tar.gz
   

5. 配置包含Java的Makefile，编译：

   ./configure --prefix=/opt/openmpi --enable-mpi-java ##不加prefix可能找不到mpi.jar
   
   make
   
   sudo make install
   

6. 配置环境变量（如 .bashrc）

   export JAVA_HOME=/root/Downloads/jdk1.8.0_161
   export JRE_HOME=${JAVA_HOME}/jre
   export MPI_HOME=/opt/openmpi
   export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib:${MPI_HOME}/lib
   export PATH=${JAVA_HOME}/bin:${MPI_HOME}/bin:$PATH
   

7. 检查是否正常运行

   import mpi.*;
   
   class ComputePi {
   
       public static void main(String args[]) throws MPIException {
   
           MPI.Init(args);
   
           int rank = MPI.COMM_WORLD.getRank(),
               size = MPI.COMM_WORLD.getSize(),
               nint = 100; // Intervals.
           double h = 1.0/(double)nint, sum = 0.0;
   
           for(int i=rank+1; i<=nint; i+=size) {
               double x = h * ((double)i - 0.5);
               sum += (4.0 / (1.0 + x * x));
           }
   
           double sBuf[] = { h * sum },
                  rBuf[] = new double[1];
   
           MPI.COMM_WORLD.reduce(sBuf, rBuf, 1, MPI.DOUBLE, MPI.SUM, 0);
   
           if(rank == 0) System.out.println("PI: " + rBuf[0]);
           MPI.Finalize();
       }
   }
   

8. 在当前路径下建立hosts文件（单机）

   localhost    slots=4 ##表示使用本机的4个进程
   

9. 编译并运行代码

   mpijavac ComputePi.java
   mpiexec --hostfile hosts -np 4 --allow-run-as-root java ComputePi
   

10. 显示结果：

    PI: 3.141600986923125
    

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