What's the best way of achieving a parallel infinite Loop?

I've gotten used to using Parallel.For() in .Net's parallel extensions as it's a simple way of parallelizing code without having to manually start and maintain threads (which can be fiddly). I'm now looking at an infinite loop (do something until I signal it to stop) that I wish to parallelize, there isn't an argument free Parallel.For() overload to do this so was wondering what the best approach here would be. In principle I could just do something like:

Parallel.For(0, int.Max) 

But I'm suspecting that might not be an expected/efficient pattern for the work partitioning logic to handle(?)

Another option is something like:

for(;;) { Parallel.For(0, 128, delegate() { // Do stuff. } } 

But that seems inelegant and may also result in inefficient work partitioning.

Right now my instinct is to do this manually by creating and maintaining my own threads, but I would be interested in getting some feedback/opinions on this. Thanks.

=== UPDATE ===

I'm using a simplified version of the code from the article in the accepted answer (I've removed the ParallelOptions parameter). Here's the code...

public class ParallelUtils { public static void While(Func<bool> condition, Action body) { Parallel.ForEach(IterateUntilFalse(condition), ignored => body()); } private static IEnumerable<bool> IterateUntilFalse(Func<bool> condition) { while (condition()) yield return true; } } 

An example usage would be:

Func<bool> whileCondFn = () => !_requestStopFlag; ParallelUtils.While(whileCondFn, delegate() { // Do stuff. }); 

3 Answers

Stephen Toub has a post about Implementing Parallel While with Parallel.ForEach.

If you (really) want something infinite then you want it on as few cores a possible. None of the Parallel.For___ would be a good choice.

What you (probably) need is a separate Thread or a Task created with the LongRunning option.

And then make it wait on a semaphore, or as a last resort call Sleep() as often as possible.

Considering that it's infinit calculus request, but you need to have some finit state on every "cycle", I would say that I would change a solution with an external for(;;) loop to execute a Parallel.ForEach(...) call on some event/state change. Like a Monitor signal, event notification, or something like that...