CpuConsumer (helper in JUnit testing that creates background CPU load)

gistfile1.java

    private static final CpuConsumer cpuConsumer = new CpuConsumer();

    @BeforeClass
    public static void prepareCpuConsumer() {
        cpuConsumer.getReady();
    }

    private static class CpuConsumer {
        final int taskCount = 2 * Runtime.getRuntime().availableProcessors();
        volatile CountDownLatch workerLatch = new CountDownLatch(1);
        volatile CountDownLatch clientLatch = new CountDownLatch(0);

        void pause() {
            if (workerLatch.getCount() == 0) {
                workerLatch = new CountDownLatch(1);
            }
        }
        void play() throws InterruptedException {
            clientLatch = new CountDownLatch(taskCount);
            workerLatch.countDown();
            assertOpenEventually(clientLatch);
        }
        void getReady() {
            final ExecutorService ex = Executors.newFixedThreadPool(taskCount);
            for (int i = 0; i < taskCount; i++) {
                ex.execute(new Runnable() {
                    double d;
                    @Override public void run() {
                        final Random rnd = new Random();
                        while (true) {
                            try {
                                workerLatch.await();
                                clientLatch.countDown();
                            } catch (InterruptedException e) {
                                System.err.println("CPU consumer interrupted: "+d);
                                return;
                            }
                            d *= Math.pow(1.001, Math.sqrt(rnd.nextInt(100) + 2));
                            if (d > 1e48) {
                                d = 1;
                            }
                        }
                    }
                });
            }
        }
    }