Stupid Pi Caculator

StupidPi.java

package funny;

import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;

/**
 *
 * @author zhouji
 */
public class StupidPi {

    static AtomicLong outerArea = new AtomicLong(0);
    
    public static void calc(long x1, long y1, long x2, long y2, long radius) {
        int rtn = 0;
        for (long x = x1; x < x2; x++) {
            for (long y = y1; y < y2; y++) {
                if (((x - radius) * (x - radius)) + ((y - radius) * (y - radius)) > radius * radius) {
                    rtn++;
                }
            }
        }
        outerArea.addAndGet(rtn);
    }

    public static void main(String[] args) throws InterruptedException {
        if( args.length == 0 ){
            System.out.println("Usage: java -cp . funny.StupidPi [radius] [split]");
            return;
        }
        final long radius = Long.parseLong(args[0]);
        long split = Integer.parseInt(args[1]);

        long start = System.nanoTime();
        long totalArea = (2 * radius) * (2 * radius);

        ExecutorService es = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
        List<Callable<Object>> todo = new ArrayList<Callable<Object>>();

        for (int x = 0; x < split; x++) {
            for (int y = 0; y < split; y++) {
                final long x1 = x * radius * 2 / split;
                final long x2 = (x + 1) * radius * 2 / split;
                final long y1 = y * radius * 2 / split;
                final long y2 = (y + 1) * radius * 2 / split;

                todo.add(Executors.callable(new Runnable() {

                    public void run() {
                        calc(x1, y1, x2, y2, radius);
                    }
                }));

            }
        }
        Object answers = es.invokeAll(todo);
        es.shutdown();
        double pi = (totalArea - outerArea.get() + 0.0) / radius / radius;
        System.out.printf("PI=%.20f\n", pi);
        System.out.println("using " + (System.nanoTime() - start) / (10000000.0));
    }

}