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TPL Dataflow and async/await vs CCR - part 4

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Today I wanted to show a number of simple examples of how to do things with TPL data-flow compared to CCR. Creating a CCR port and posting and then receiving on it asynchronously is one fundamental scenario in CCR. This is what it looks like with TPL data-flow:

  1: var port = new BufferBlock<int>();
 2: port.Post(42);
 3: int result = await port.ReceiveAsync();

If you want to explicitly extract data from a port this is how you would do it:

  4: int item;
 5: if (port.TryReceive(out item))
 6: {
 7:     ProcessItem(item);
 8: }

Very similar to CCR which would just use the Port.Test method on line X. Remember how we in the test coded needed a synchronous way to receive data on a port using ManualResetEvents. Much easier with TPL data-flow:

  9: int item = port.Receive();

One larger difference is that in CCR concurrent processing of handlers on ports is the default while in TPL data-flow the default is to process one item at the time. This is how you can change that:

  10: var port = new ActionBlock<int>(
 11:     item => ProcessItem(item), 
 12:     new DataflowBlockOptions 
 13:         { MaxDegreeOfParallelism = Environment.ProcessorCount });

It is also very easy to introduce interleaving as in CCR. That is limit the processing across multiple ports. It can look something like this:

  14: var options = new DataflowBlockOptions() { 
 15:     TaskScheduler = 
 16:         new ConcurrentExclusiveSchedulerPair().ExclusiveScheduler
 17: };
 18: var p1 = new ActionBlock<int>(item => ProcessItem(item), options);
 19: var p2 = new ActionBlock<int>(item => ProcessItemDifferent(item), options);

These are just a few differences that should get you started. Bottom line is that if you're used to CCR it is very easy to switch over to use TPL data-flow if you ask me.

Comments

  • Anonymous
    December 25, 2011
    Hi, thank you again for yet another great post. The TPL syntax is much more verbose and harder to setup. The way on creating the interleave was not so apparent to me coming from CCR programming model. Keep up the great posts. Ido