The Big Programming Thread - Page 806

import java.util.Random;

public class MathWithMultipleThreads {

	private static Random random = new Random();
	private static int HEIGHT = 1000;
	private static int WIDTH = 1000;

	private static double[][] makeArray(int height, int width) {
		double[][] answer = new double[height][width];
		for (int row = 0; row < height; row++) {
			for (int col = 0; col < width; col++) {
				answer[row][col] = random.nextDouble();
			}
		}
		return answer;
	}

	public static void main(String[] args) throws InterruptedException {
		double[][] array = makeArray(HEIGHT, WIDTH);
		long start = System.nanoTime();

		Thread[] threads = new Thread[HEIGHT];

		for (int i = 0; i < HEIGHT; i++) {
			threads[i] = new Thread(new ProcessRow(array[i]));
			threads[i].start();
		}

		for (int i = 0; i < HEIGHT; i++) {
			threads[i].join();
		}

		long end = System.nanoTime();
		System.out.println((end - start) / 1000000000.0);
	}
}

public class ProcessRow implements Runnable {

	double[] row;
		
	public ProcessRow(double[] row) {
		this.row = row;
	}
		
	@Override
	public void run() {
		for (int i = 0; i < row.length; i++){
			row[i] = Math.sqrt(row[i]);
		}
	}	
}