RE: [Caml-list] Efficient OCaml multicore -- roadmap?

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Am Mittwoch, den 20.04.2011, 20:23 +0100 schrieb Jon Harrop:
> Martin wrote:
> > On 03/25/11 08:44, Hugo Ferreira replied:
> > > I'll stick to my guns here. It simply makes solving certain problem
> > > unfeasible. Point in case: I work on machine learning algorithms. I
> > > use large data-structures that must be processed (altered) in order to
> > > learn. Because these data-structures are large it become impractical
> > > to copy this to a process every time I start off a new "thread".
> > 
> > The solution would be to use get/set via a message-passing interface.
> 
> The main objective when parallelizing a program is to remove focal points because they are sources of contention. Funnelling all IO through a single getter/setter would add a focal point and, most likely, destroy scalability.
> 
> > From my purely speculative perspective, it seems unavoidable that message-
> > passing happens at some level in order to keep a shared data structure in sync
> > between a large number of processors. In other words, any access to a shared
> > data structure requires some physical copy no matter what the programming
> > language makes it look like.
> 
> Yes. The hardware maintains the illusion of shared memory so the programmer only need optimize on the basis of an accurate cost model. There is no need to burden the programmer with message passing and manual memory management.

I don't understand this last sentence. Message passing is just an
abstract concept (i.e. an interface) which can e.g. be implemented with
a shared buffer (or the illusion thereof) or other data structure that
decouples sender and receiver processes. Are you against using the right
interfaces when they are appropriate? We don't want to burden the
programmer with too low-level details, do we?

Gerd


> 
> Cheers,
> Jon.
> 
> 
> 
> 


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