Linux Java OpenMPI 安装

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

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

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

make

sudo make install

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

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();
}
}

localhost    slots=4 ##表示使用本机的4个进程

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

PI: 3.141600986923125