Sequential Task Tutorial

This tutorial will demonstrate how a ThimbleExecutor executes sequential tasks. The code below runs a sequential task in a 4-thread ThimbleExecutor.

• ThimbleExecutor version
• Standard Executor version
• Conclusion

ThimbleExecutor version

:::java
public class TestSequential
{
    public static void main(String[] args) throws Exception
    {
        Executor executor = new ThimbleExecutor(4);
        final int count = 10;
        final CountDownLatch latch = new CountDownLatch(count * 2);
        for (int i = 0; i < count; i++)
        {
            final int myCount = i;

            executor.execute(new ISequentialRunnable()
            {
                @Override
                public void run()
                {
                    System.out.println("HelloWorld (context 1) " + myCount);
                    latch.countDown();
                }

                @Override
                public Object context()
                {
                    return "context1";
                }
            });

            executor.execute(new ISequentialRunnable()
            {
                @Override
                public void run()
                {
                    System.out.println("HelloWorld (context 2) " + myCount);
                    latch.countDown();
                }

                @Override
                public Object context()
                {
                    return "context2";
                }
            });
        }
        latch.await();        
    }
}

The output demonstrates that the tasks are executed in order. Notice that there is some inter-leaving for the execution of the sequential tasks between context 1 and context 2 but that both contexts have their tasks executed in sequence.

HelloWorld (context 1) 0
HelloWorld (context 1) 1
HelloWorld (context 2) 0
HelloWorld (context 1) 2
HelloWorld (context 2) 1
HelloWorld (context 1) 3
HelloWorld (context 2) 2
HelloWorld (context 1) 4
HelloWorld (context 2) 3
HelloWorld (context 1) 5
HelloWorld (context 2) 4
HelloWorld (context 1) 6
HelloWorld (context 2) 5
HelloWorld (context 1) 7
HelloWorld (context 2) 6
HelloWorld (context 1) 8
HelloWorld (context 2) 7
HelloWorld (context 1) 9
HelloWorld (context 2) 8
HelloWorld (context 2) 9

Standard Executor version

Compare this with using a standard multi-thread executor

:::java
public class TestSequentialWithStandardExecutor
{
    public static void main(String[] args) throws Exception
    {
        Executor executor = Executors.newFixedThreadPool(4);
        final int count = 10;
        final CountDownLatch latch = new CountDownLatch(count * 2);
        for (int i = 0; i < count; i++)
        {
            final int myCount = i;

            executor.execute(new ISequentialRunnable()
            {
                @Override
                public void run()
                {
                    System.out.println("HelloWorld (context 1) " + myCount);
                    latch.countDown();
                }

                @Override
                public Object context()
                {
                    return "context1";
                }
            });

            executor.execute(new ISequentialRunnable()
            {
                @Override
                public void run()
                {
                    System.out.println("HelloWorld (context 2) " + myCount);
                    latch.countDown();
                }

                @Override
                public Object context()
                {
                    return "context2";
                }
            });
        }
        latch.await();        
    }
}

The output shows that the tasks are executed non-sequentially.

HelloWorld (context 1) 0
HelloWorld (context 2) 0
HelloWorld (context 1) 2
HelloWorld (context 1) 3
HelloWorld (context 2) 2
HelloWorld (context 1) 4
HelloWorld (context 2) 4
HelloWorld (context 2) 1
HelloWorld (context 2) 5
HelloWorld (context 2) 3
HelloWorld (context 1) 6
HelloWorld (context 1) 5
HelloWorld (context 2) 7
HelloWorld (context 1) 8
HelloWorld (context 1) 1
HelloWorld (context 2) 8
HelloWorld (context 1) 7
HelloWorld (context 2) 6
HelloWorld (context 2) 9
HelloWorld (context 1) 9

Conclusion

This demonstrates that a single ThimbleExecutor could be used to handle sequential tasks. In situations where tasks for multiple contexts need to be executed in sequence, rather than having a single-thread per context, a single multi-thread ThimbleExecutor can be used.