高分多線程問題

Ganymede 2013-04-24 07:54:46

大家好，

有关knight's tour的問題現在我想用多線程幷發該如何解決主要是用到生產者消費者以及工作隊列。要求worker不斷從工作隊列中獲得Path p 然後進行處理如果不清楚knight's tour的可以看下我下面的代碼，只要把這段代碼改成幷發執行的就OK了，時間在26號中午之前。先謝謝了！！

// Find a *single* closed knight's tour 

// (Sequential & iterative version, not optimised)



import java.util.*;



class Position {

	

	static final int numRows = 3; // number of rows on board

	static final int numCols = 10; // number of columns on board

	

	static final Position end1 = new Position(1,2); // possible end positions (start is (0,0) 

	static final Position end2 = new Position(2,1); // other possible end position 

	

	private int row; // row number, o<=i<numRows

	private int col;  // column number, o<=j<numCols





	Position(int row0,int col0) {

		row = row0; col = col0;

	}

	

	public boolean equals(Object obj) { // compare with another position

		if (obj==null) return false;

		Position p = (Position) obj;

		return (p.row==row && p.col==col);

	}



	Position[]  knightMoves() { //list of knight's possible moves from here

		Position[] temp = new Position[8];

		int count = 0; // temp[0..count-1] holds results

		int[] xStep = {2, 2, -2, -2, 1, 1, -1, -1}; // potential moves are (row+yStep[k],col+xStep[k]) for each index k

		int[] yStep = {1, -1, 1, -1, 2, -2, 2, -2}; 

		for (int k=0; k<xStep.length; k++) { // check that each potential move stays on board

			int x = row+yStep[k];

			int y = col+xStep[k];

			if (0<=x && x<numCols && 0<=y && y<numRows) {

				temp[count] = new Position(x,y); count++;

			}

		}

		Position[]  result = new Position[count];

		for (int k=0; k<count; k++)

			result[k] = temp[k];

		return result;

	}

	

	void putPosition() { // print position

		System.out.print("("+row+","+col+")");

	}

}



class Path {  // non-empty path of Position's

	

	private Position start;  // one end position in path (other is (0,0))

	private Path next;		 // path following start node (may be null) 

	private int pathLength;  // length of path

	

	Path(Position start0, Path next0) {	

		start = start0; next = next0;

		if (next==null)

			pathLength = 1;

		else

			pathLength = 1 + next.pathLength;

	}

	

	boolean contains(Position p) { // does p occur in this path?

		if (start.equals(p)) return true;

		else if (next==null) return false;

		else return next.contains(p);

	}

	



	Position[]  pathMoves() { // new positions to extend path

		return start.knightMoves();

	}



	boolean pathComplete() { // does the path cover the entire board?

		int tourLength = Position.numRows*Position.numCols;

		return pathLength == tourLength;

	}

	

	boolean pathClosed() { // is the path (assumed complete) closed?

		return start.equals(Position.end1) || start.equals(Position.end2);

	}

	

	void putPath() { // print path

		start.putPosition();

		if (next!=null) {

			System.out.print(":");

			next.putPath();

		}

	}

	

}



class KnightsTourSingleItSeq {   

	    

    private static void knightsTour() { 

    	LinkedList<Path> workQ = new LinkedList<Path>();

    	workQ.add(new Path(new Position(0,0), null));

    	while (!workQ.isEmpty()) {       		       

    		Path path = workQ.removeLast(); 

    		Position[] moves = path.pathMoves();

    		for (Position pos : moves) {

    			if (!path.contains(pos)) {    				

					Path newPath = new Path(pos, path);

    				if (newPath.pathComplete()) {

    					if (newPath.pathClosed()) 

    						newPath.putPath();

    						System.out.println();

    						return;

    				}

    				else workQ.add(newPath);

    			}

    		}

    	}    	  

    }



	public static void main(String[] args) {

		long startTime = System.nanoTime();		

        knightsTour(); 

		long endTime = System.nanoTime();

		long time = (endTime-startTime)/1000000;

		System.out.println("Running time = " + time);

	}

}