Does F# provide you automatic parallelism?

Question

By this I meant: when you design your app side effects free, etc, will F# code be automatically distributed across all cores?

Answer 1

Well, you have your answer, but I just wanted to add that I think this is the most significant limitation of F# stemming from the fact that it is a hybrid imperative/functional language.

I would like to see some extension to F# that declares a function to be pure. That is, it has no side-effects that are not denoted by the function's type. The idea would be that a function is pure only if it references other "known-pure" functions. Of course, this would only be useful if it were then possible to require that a delegate passed as a function parameter references a pure function.

Answer 2

F# does not make it automatic, it just makes it easy.

Yet another chance to link to Luca's PDC talk. Eight minutes starting at 52:20 are an awesome demo of F# async workflows. It rocks!

Answer 3

Like the others mentioned, F# will not automatically scale across cores and will still require a framework such as the port of ParallelFX that Josh mentioned.

F# is commonly associated with potential for parallel processing because it defaults to objects being immutable, removing the need for locking for many scenarios.

Answer 4

My understanding is that it won't but Parallel Extensions is being modified to make it consumable by F#. Which won't make it automatically multi-thread it, should make it very easy to achieve.

Answer 5

No it will not. You must still explicitly marshal calls to other threads via one of the many mechanisms supported by F#.

Answer 6

On purity annotations: Code Contracts have a Pure attribute. I remember hearing the some parts of the BCL already use this. Potentially, this attribute could be used by parallellization frameworks as well, but I'm not aware of such work at this point. Also, I' not even sure how well code contacts are usable from within F#, so a lot of unknowns here.

Still, it will be interesting to see how all this stuff comes together.