76 строки
2.0 KiB
Java
76 строки
2.0 KiB
Java
/*
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* Copyright (c) 2011 Cisco Systems, Inc. All rights reserved.
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*
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* Simple ring test program
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*/
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import mpi.* ;
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class Ring {
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static public void main(String[] args) throws MPIException {
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MPI.Init(args) ;
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int source; // Rank of sender
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int dest; // Rank of receiver
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int tag=50; // Tag for messages
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int next;
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int prev;
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int message[] = new int [1];
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int myrank = MPI.COMM_WORLD.getRank() ;
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int size = MPI.COMM_WORLD.getSize() ;
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/* Calculate the rank of the next process in the ring. Use the
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modulus operator so that the last process "wraps around" to
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rank zero. */
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next = (myrank + 1) % size;
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prev = (myrank + size - 1) % size;
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/* If we are the "master" process (i.e., MPI_COMM_WORLD rank 0),
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put the number of times to go around the ring in the
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message. */
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if (0 == myrank) {
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message[0] = 10;
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System.out.println("Process 0 sending " + message[0] + " to rank " + next + " (" + size + " processes in ring)");
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MPI.COMM_WORLD.send(message, 1, MPI.INT, next, tag);
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}
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/* Pass the message around the ring. The exit mechanism works as
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follows: the message (a positive integer) is passed around the
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ring. Each time it passes rank 0, it is decremented. When
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each processes receives a message containing a 0 value, it
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passes the message on to the next process and then quits. By
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passing the 0 message first, every process gets the 0 message
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and can quit normally. */
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while (true) {
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MPI.COMM_WORLD.recv(message, 1, MPI.INT, prev, tag);
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if (0 == myrank) {
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--message[0];
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System.out.println("Process 0 decremented value: " + message[0]);
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}
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MPI.COMM_WORLD.send(message, 1, MPI.INT, next, tag);
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if (0 == message[0]) {
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System.out.println("Process " + myrank + " exiting");
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break;
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}
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}
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/* The last process does one extra send to process 0, which needs
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to be received before the program can exit */
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if (0 == myrank) {
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MPI.COMM_WORLD.recv(message, 1, MPI.INT, prev, tag);
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}
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MPI.Finalize();
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}
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}
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