Concurrency

[Simon Marlow]

On 31 March 2006 13:41, John Meacham wrote:

> I have tried to summarize the current thinking into a proposal on the
> wiki.
> 
>
http://haskell.galois.com/cgi-bin/haskell-prime/trac.cgi/wiki/Concurrenc
y
> 
> I split it into 3 parts.
> 
> the standard - all haskell' compilers must implement
> 
> optional preemption - ability to preempt pure code, fairness
> guarentees, interleaved evaluation operators (merge, nmerge)
> 
> optional OS threads - bound threads, SMP, reentrant concurrent FFI
> calls supported.
> 
> comment or modify it at will.

Great.  Apart from my misgivings about allowing cooperative scheduling
at all, here's a few comments on the proposal:

  - I wouldn't include threadWaitRead, threadWaitWrite,
    or threadDelay at all.  These can all be implemented using
    FFI, so don't belong in the concurrency library.  Their
    presence is largely historical.

  - yield bothers me a little.  If it weren't for cooperative
    systems, yield would be semantically a no-op, because the
    no-starvation guarantee means you never need it for
    correctness.  I think it's ok, just a bit unsettling.

  - In the optional OS threads section it says "allows multiple
    haskell threads to run at once" - actually you can provide
    all that without allowing multiple haskell threads to run
    at once, eg. ghc-6.4.1 with -threaded.  I'll modify it.

Cheers,
	Simon