Question

I used multiple threads in a few programs, but still don’t feel very comfortable about it.

What multi-threading libraries for C#/.NET are out there and which advantages does one have over the other?

By multi-threading libraries I mean everything which helps make programming with multiple threads easier.

What .NET integratet (i.e. like ThreadPool) do you use periodically? Which problems did you encounter?

Answer 1

There are various reasons for using multiple threads in an application:

• UI responsiveness
• Concurrent operations
• Parallel speedup

The approach one should choose depends on what you’re trying to do. For UI responsiveness, consider using BackgroundWorker, for example.

For concurrent operations (e.g. a server: something that doesn’t have to be parallel, but probably does need to be concurrent even on a single-core system), consider using the thread pool or, if the tasks are long-lived and you need a lot of them, consider using one thread per task.

If you have a so-called embarrassingly parallel problem that can be easily divided up into small subproblems, consider using a pool of worker threads (as many threads as CPU cores) that pull tasks from a queue. The Microsoft Task Parallel Library (TPL) may help here. If the job can be easily expressed as a monadic stream computation (i.e. with a query in LINQ with work in transformations and aggregations etc.), Parallel LINQ (same link) which runs on top of TPL may help.

There are other approaches, such as Actor-style parallelism as seen in Erlang, which are harder to implement efficiently in .NET because of the lack of a green threading model or means to implement same, such as CLR-supported continuations.