我在用 Java 编写多线程算法时遇到了一些问题。这是我所拥有的：
public class NNDFS implements NDFS {
//Array of all worker threads
private Thread[] threadArray;
//Concurrent HashMap containing a mapping of graph-states and
//algorithm specific state objects (NDFSState)
private ConcurrentHashMap<State, NDFSState> stateStore;
//Whether the algorithm is done and whether a cycle is found
private volatile boolean done;
private volatile boolean cycleFound;
/**
Constructor that creates the threads, each with their own graph
@param file The file from which we can create the graph
@param stateStore Mapping between graph-states and state belonging to our algorithm
@param nrWorkers Number of working threads we need
*/
public NNDFS(File file, Map<State, NDFSState> stateStore, int nrWorkers) throws FileNotFoundException {
int i;
this.stateStore = new ConcurrentHashMap<State, NDFSState>(stateStore);
threadArray = new Thread[nrWorkers];
for(i=0;i<nrWorkers;i++){
Graph graph = GraphFactory.createGraph(file);
threadArray[i] = new Thread(new NDFSRunnable(graph, i));
}
}
/**
Class which implements a single thread running the NDFS algorithm
*/
class NDFSRunnable implements Runnable{
private Graph graph;
//Neccesary as Java apparently doesn't allow us to get this ID
private long threadId;
NDFSRunnable(Graph graph, long threadId){
this.graph = graph;
this.threadId = threadId;
}
public void run(){
try {
System.out.printf("Thread id = %d\n", threadId);
//Start by executing the blue DFS for the first graph
mcdfsBlue(graph.getInitialState(), threadId);
} catch (CycleFound e) {
//We must catch all exceptions that are thrown from within our thread
//If exceptions "exit" the thread, the thread will silently fail
//and we dont want that. We use 2 booleans instead, to indicate the status of the algorithm
cycleFound = true;
}
//Either the algorithm was aborted because of a CycleFound exception
//or we completed our Blue DFS without finding a cycle. We are done!
done = true;
}
public void mcdfsBlue(State s, long id) throws CycleFound {
if(done == true){
return;
}
//System.out.printf("Thread %d begint nu aan een dfsblue\n", id);
int i;
int counter = 0;
NDFSState state = stateStore.get(s);
if(state == null){
state = new NDFSState();
stateStore.put(s,state);
}
state.setColor(id, Color.CYAN);
List<State> children = graph.post(s);
i = state.incNextBlue();
while(counter != children.size()){
NDFSState child = stateStore.get(children.get(i%children.size()));
if(child == null){
child = new NDFSState();
stateStore.put(children.get(i % children.size()),child);
}
if(child.getLocalColor(id) == Color.WHITE && !child.isRed()){
mcdfsBlue(children.get(i % children.size()), id);
}
i++;
counter++;
}
if(s.isAccepting()){
state.incRedDFSCount();
mcdfsRed(s, id);
}
state.setColor(id, Color.BLUE);
}
public void mcdfsRed(State s, long id) throws CycleFound {
if(done == true){
return;
}
int i;
int counter = 0;
NDFSState state = stateStore.get(s);
state.setPink(id, true);
List<State> children = graph.post(s);
i = state.incNextRed();
while(counter != children.size()){
NDFSState child = stateStore.get(children.get(i%children.size()));
if(child == null){
child = new NDFSState();
stateStore.put(children.get(i%children.size()),child);
}
if(child.getLocalColor(id) == Color.CYAN){
throw new CycleFound();
}
if(!child.isPink(id) && !child.isRed()){
mcdfsRed(children.get(i%children.size()), id);
}
i++;
counter++;
}
if(s.isAccepting()){
state.decRedDFSCountAndWait();
}
state.setRed();
state.setPink(id, false);
}
}
public void init() {}
public void ndfs() throws Result {
int i;
done = false;
cycleFound = false;
for(i=0;i<threadArray.length;i++){
System.out.printf("Launch thread %d\n",i);
threadArray[i].run();
}
try {
for(i=0;i<threadArray.length;i++){
threadArray[i].join();
}
} catch (InterruptedException e) {
}
//We want to show the result by throwing an exception (weird, but yeah :-/)
if (cycleFound) {
throw new CycleFound();
} else {
throw new NoCycleFound();
}
}
}
但是，当我运行它时，似乎第一个线程被调用，完成，然后下一个被调用等等。我显然想要的是所有线程同时启动！否则该算法几乎没有用......
感谢您的时间/帮助！
问候，
莱纳斯