package com.whirlycott.samples;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * 
 * How much of a difference does the volatile keyword make?
 * 
 * Public domain.
 * 
 * @author pjacob
 *
 */
public class VolatileTest {

	//A normal long.
	private static long normalCount = 0;
	
	//A volatile long.
	private static volatile long volatileCount = 0;

	//Number loops to use.
	private static final long LOOP_COUNT = 10 * 1000 * 1000;
	
	//How many threads should we use?
	private static final long THREAD_COUNT = 32;
	
	
	public static void main(String[] args) throws InterruptedException {
		
		final List threads = new ArrayList();
		
		for (int n=0; n < THREAD_COUNT; n++) {
			
			//Make a little anonymous thread.
			final Thread t = new Thread("Thread: " + n) {
				public void run() {
					for (long i = 0; i < LOOP_COUNT; i++) {
						normalCount++;
						volatileCount++;
					}
				}
			};
			
			//Add the threads to a List so we can wait for them (need a ref to do this)
			threads.add(t);
			
			//Start up the thread
			t.start();
			
		}
		
		System.out.println("All threads started.");
		
		//Now, wait for the threads to complete
		for (final Iterator i = threads.iterator(); i.hasNext(); ) {
			final Thread t = (Thread)i.next();
			t.join();
		}
		
		System.out.println("Number of loops:   " + ( THREAD_COUNT * LOOP_COUNT));
		System.out.println("Non-volatile long: " + normalCount);
		System.out.println("Volatile long:     " + volatileCount);
		
	}
}