我用Java编写了一个程序，它在单线程中调用OpenMPI进行通信。 Isend / recv 用于防止死锁。调用者调用send方法，然后将所有发送请求放入队列中。网络线程从队列获取请求发送。
class NetworkThread extends Thread {
private final ConcurrentLinkedQueue<SendRequest> sendQueue = new ConcurrentLinkedQueue<>();
private final List<Request> activeSends = new LinkedList<>();
private final List<RecvRequest> recvList = new LinkedList<>();
private volatile boolean shutdown;
@Override
public void run() {
System.out.println("network thread started");
try {
loop();
} catch (MPIException e) {
e.printStackTrace();
}
}
void loop() throws MPIException {
while (!shutdown) {
Status status = MPI.COMM_WORLD.iProbe(MPI.ANY_SOURCE, MPI.ANY_TAG);
if (status != null) {
int source = status.getSource();
int tag = status.getTag();
int sizeInBytes = status.getCount(MPI.BYTE);
ByteBuffer buffer = MPI.newByteBuffer(sizeInBytes);
MPI.COMM_WORLD.recv(buffer, sizeInBytes, MPI.BYTE, source, tag);
byte[] data = new byte[sizeInBytes];
buffer.get(data);
RecvRequest recvRequest = new RecvRequest(data, source, tag);
synchronized (recvList) {
recvList.add(recvRequest);
}
}
SendRequest sendRequest;
while ((sendRequest = sendQueue.poll()) != null) {
byte[] data = sendRequest.getData();
ByteBuffer buffer = MPI.newByteBuffer(data.length);
buffer.put(data);
Request request = MPI.COMM_WORLD.iSend(buffer, data.length, MPI.BYTE, sendRequest.getDest(), sendRequest.getTag());
synchronized (activeSends) {
activeSends.add(request);
}
}
//delete sent record
synchronized (activeSends) {
Iterator<Request> iterator = activeSends.iterator();
while (iterator.hasNext()) {
Request request = iterator.next();
if (request.test())
iterator.remove();
}
}
}
}
public void send(byte[] data, int dest, int tag) {
SendRequest sendRequest = new SendRequest(data, dest, tag);
sendQueue.add(sendRequest);
}
public byte[] read(int source, int tag) {
byte[] data;
while ((data = tryRead(source, tag)) == null) {
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return data;
}
public byte[] tryRead(int source, int tag) {
byte[] data = null;
synchronized (recvList) {
Iterator<RecvRequest> iterator = recvList.iterator();
while (iterator.hasNext()) {
RecvRequest recvRequest = iterator.next();
if (recvRequest.getSource() == source && recvRequest.getTag() == tag) {
iterator.remove();
data = recvRequest.getData();
break;//just get one
}
}
}
return data;
}
public void shutdown() {
shutdown = true;
//waiting for all sent
synchronized (activeSends) {
while (activeSends.size() > 0)
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class SendRequest {
private byte[] data;
private int dest;
private int tag;
SendRequest(byte[] data, int dest, int tag) {
this.data = data;
this.dest = dest;
this.tag = tag;
}
public int getTag() {
return tag;
}
public int getDest() {
return dest;
}
public byte[] getData() {
return data;
}
}
class RecvRequest {
private byte[] data;
private int source;
private int tag;
RecvRequest(byte[] data, int source, int tag) {
this.data = data;
this.source = source;
this.tag = tag;
}
public int getTag() {
return tag;
}
public int getSource() {
return source;
}
public byte[] getData() {
return data;
}
}
我还写了一个测试用例，它在随机时间间隔内为每个进程实现了五次广播数据（除了我自己和主人）。希望所有进程都完成发送/接收任务然后退出。
public class BroadcastTest {
private static final int TAG_MPI = 123;
static int rank;
static String host;
static {
try {
host = InetAddress.getLocalHost().getHostName();
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws MPIException, InterruptedException, UnknownHostException {
MPI.Init(args);
int rank = MPI.COMM_WORLD.getRank();
int size = MPI.COMM_WORLD.getSize();
BroadcastTest.rank = rank;
if (rank == 0) {
System.out.println(String.format("total %d machines", size));
System.out.println("master started");
} else {
NetworkThread networkThread = new NetworkThread();
networkThread.start();
Thread sendTh = new Thread(() -> {
for (int i = 0; i < 5; i++) {
try {
Thread.sleep((long) (Math.random() * 1000)); //send data five times in random interval
} catch (InterruptedException e) {
e.printStackTrace();
}
for (int machineId = 1/* skip master */; machineId < size; machineId++) {
if (machineId == rank) continue;//skip myself
networkThread.send(new byte[4096], machineId, TAG_MPI); //send 4K bytes data
}
}
});
//receive data
Thread recvTh = new Thread(() -> {
for (int i = 0; i < 5; i++) {
for (int machineId = 1; machineId < size; machineId++) {
if (machineId == rank) continue;
byte[] bytes = networkThread.read(machineId, TAG_MPI);
}
}
});
sendTh.start();
recvTh.start();
sendTh.join();
recvTh.join();
networkThread.shutdown();
networkThread.join();
}
System.out.println(String.format("%s exit", host));
MPI.Finalize();
}
}
命令行：
/home/gongsf/openmpi-2.1.2/bin/mpirun --prefix /home/gongsf/openmpi-2.1.2 -bycore -nooversubscribe -machinefile /home/gongsf/JavaMPI/myhosts /home/gongsf/jdk1.8.0_144/bin/java -classpath /home/gongsf/JavaMPI/lib/*:/home/gongsf/JavaMPI/out/production/JavaMPI BroadcastTest
问题：此程序在较低的流程中正常工作，例如槽= 4。但是当增加要发送的插槽或数据大小时，程序偶尔会进入死锁状态。我试图改变OpenMPI版本（3.0,2.1.2,1.7.5），但似乎不起作用。