threadtest.java

这个是一个计算表达式的java包

/*
Created 2 Aug 2006 - Richard Morris
*/
package com.singularsys.jepexamples.diagnostics;

import com.singularsys.jep.ComponentSet;
import com.singularsys.jep.EvaluationException;
import com.singularsys.jep.Jep;
import com.singularsys.jep.JepException;
import com.singularsys.jep.ParseException;
import com.singularsys.jep.Variable;
import com.singularsys.jep.misc.LightWeightComponentSet;
import com.singularsys.jep.parser.Node;
import com.singularsys.jep.walkers.SerializableExpression;

/**
 * Testing thread safety, using Taylor approximation to ln(x).
 * @author Richard Morris
 *
 */
public class ThreadTest {

	class EvaluationThread extends Thread {
		Jep myJep=null;
		Node myExpression;
		double min,max;
		int itts;
		Variable myVar;
		double results[];
		int n;
		public EvaluationThread(Jep localJep,SerializableExpression se,
			double minValue,double maxValue,int numItts,int threadNum) 
			throws JepException
		{
			min = minValue;
			max = maxValue;
			itts = numItts;
			n=threadNum;
			myJep = localJep; //(Jep) ois.readObject();
			//SerializableExpression se = (SerializableExpression) ois.readObject(); 
			myExpression = se.toNode(myJep);
			myVar = myJep.addVariable("x");
			results = new double[numItts];
		}
		
		public void run() {
		    System.out.println("Thread "+n+" started");
		    try {
			for(int i=0;i<itts;++i)
			{
			    double value = min+(max-min)*((double)i)/(itts-1);
			    myVar.setValue(value);
			    Object resObj = myJep.evaluate(myExpression);
			    results[i] = ((Double) resObj);
			}
		    } catch (EvaluationException e) {
			e.printStackTrace();
		    }
		    System.out.println("Thread "+n+" finished");
		}

		public double[] getResults() {
		    return results;
		}
	}
	
	Jep baseJep;
	
	void printMem() {
		Runtime rt = Runtime.getRuntime();
//		System.out.println(
//			"Total "+rt.totalMemory()+" free "+rt.freeMemory()+" max "+rt.maxMemory());
		System.out.println("Used mem "+ (rt.totalMemory()-rt.freeMemory()));
	}
	
	public ThreadTest() {
	    baseJep = new Jep();
	}
	
	public String getExpression(int nDeriv) {
		StringBuilder sb = new StringBuilder();
		for(int i=1;i<=nDeriv;++i)
		{
			if(i%2==0)
				sb.append("-");
			else
				sb.append("+");
			sb.append("x^"+i+"/"+i);
		}
		return sb.toString();
	}
	
	public void go(String expression,
		int nThreads,int nItts,
		double minValue,double maxValue) throws JepException
	{
		Node base = baseJep.parse(expression);
		SerializableExpression se = new SerializableExpression(base);
		EvaluationThread et[] = new EvaluationThread[nThreads];
		printMem();
		Jep threadJeps[] = new Jep[nThreads];
		for(int i=0;i<nThreads;++i)
		{
			ComponentSet cs = new LightWeightComponentSet(baseJep);
			threadJeps[i] = new Jep(cs); //(Jep) ois.readObject();
		}
		printMem();

		for(int i=0;i<nThreads;++i)
		{
			et[i] = new EvaluationThread(threadJeps[i],se,minValue,maxValue,nItts,i);
		}
		printMem();

		for(int i=0;i<nThreads;++i)
		    et[i].start();

		// now wait for threads to finish
		for(int i=0;i<nThreads;++i) {
		    try {
			et[i].join();
		    } catch (InterruptedException e) {
			System.out.println("thread "+i+" interrupted "+e.getMessage());
		    }
		}
		
		// check same results from each thread
		for(int i=1;i<nThreads;++i)
		    for(int j=0;j<nItts;++j) 
			if(et[0].results[j] != et[i].results[j])
			    throw new ParseException("Error values do not match ");
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ThreadTest tt = new ThreadTest();
		String s = tt.getExpression(20);
		try {
		    tt.go(s,25,10000,-1.0,1.0);
		} catch (JepException e) {
		    System.out.println(e.getMessage());
		}
	}

}