Useful Abstractions Enabled with ContinueWith

re: Useful Abstractions Enabled with ContinueWith

art_scott@msn.com — Fri, 25 Jul 2008 02:16:40 GMT

Hi toub.

When I get a 42 core multi-core system...

I'd like to watch 42 HD-DVD's in 42 windows at the same time...

Is ContinueWith a useful abstraction for that scenario? (Maybe I need 1024 cores?)

Thanks,

art

re: Useful Abstractions Enabled with ContinueWith

Chernichkin Stanislav — Fri, 25 Jul 2008 16:41:37 GMT

Hi toub!

Currently I’m writing network communication application which relies on .net APM (IAsyncResult + Begin... End… methods). I use this pattern because I want to minimize thread blocking. Threads are quite expensive, so I can’t allow thread just wait for response from remote system wasting system resources. The problem is that my code becomes too complicated quickly, especially when I introduce task cancelation, fault handling and time-outs. Currently I’m looking for simplified pattern to replace .net APM and, probably, standard library, written by someone else (ok, MS will suite me well :). Parallel Extensions to the .NET Framework seems to be good choice but I’m steel missing some functionality.

The first is the Task in non-blocking scenarios. In “Wrapping an APM implementation with Future<T>” you wrote how to use Future to implement non-blocking APM pattern wrapping, but lot of methods does not produce result, so using Task for wrapping would be preferred.

Second is Future chaining. Consider I have some service, which should process request sequentially in some order (FIFO in most cases, but more complex scenarios also possible). I need to implement non-blocking post method, which will schedule request for execution. Also, due to limited numbers of threads, I can’t allocate separate thread for each service, thread should be allocated only when it needed and released when work is done. Currently I’m using something like this:

public Future<Result> Process()

{

var newFuture = Future<Result>.Create();

var prevFuture = Interlocked.Exchange(ref PrevFuture, newFuture);

if (prevFuture != null)

prevFuture.ContinueWith(delegate

{

// here “if (!newFuture.IsCanceled)” may be placed

OnProcess(newFuture);

});

else

OnProcess(newFuture);

return newFuture;

}

where OnProcess() starts non-blocking APM method and subscribes to result. As you can see in this approach nearly unnecessary short running task created, the only work of which is to start non-blocking asynchronous operation. It would be nice to have some standard method to chain APM method wrappers.

Waiting for Tasks

Parallel Programming with .NET — Wed, 06 Aug 2008 04:52:13 GMT

Parallel Extensions makes it easy to wait for Tasks to complete.  Task exposes a Wait method, which

re: Useful Abstractions Enabled with ContinueWith

Urs Gleim — Mon, 15 Dec 2008 15:56:38 GMT

Hi toub,

regarding your ContinueWhenAll example.

Why don't you just do this?:

Task.WaitAll(t1, t2);

Task.Create(delegate { Console.WriteLine("t1 and t2 finished"); });

What is the difference to your ContinueWhenAll?

Cheers, Urs

re: Useful Abstractions Enabled with ContinueWith

wekempf — Wed, 31 Dec 2008 23:07:07 GMT

Urs,

WaitAll blocks, while ContinueWhenAll does not. ContinueWhenAll just schedules a delegate to run when all tasks are complete, and then continues on, while WaitAll blocks the current thread until all the tasks are complete. This is an important distinction.

re: Useful Abstractions Enabled with ContinueWith

Alberto Fuentes — Sat, 07 Feb 2009 17:20:37 GMT

.Net 4.0 is going to be very interesting to exploit multicore processors. However, do you know a due date?

In the meantime, I began working with multicore programming using current C# 2008, as I need more performance in some batch processes.

I bought the book for beginners by Packt Publishing: "C# 2008 and 2005 Threaded Programming: Beginner’s Guide", by Gaston C. Hillar - http://www.packtpub.com/beginners-guide-for-C-sharp-2008-and-2005-threaded-programming/book

The book covers a few chapters about Parallel Extensions. However, it also teaches to use the current threading model. I am achieving amazing results with my dual core CPU.

Recommended for those who are trying to program for multicore CPUs.

I can't wait to see Visual Studio 2010 in the market.

But, please, provide a date!!!