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

[Eray Ozkural <examachine@gmail.com>]

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On Sat, Apr 23, 2011 at 4:47 PM, Alexy Khrabrov <deliverable@gmail.com>wrote:

>
> On Apr 23, 2011, at 6:17 AM, Eray Ozkural wrote:
>
> > I don't really care what others say, but to prove that this has any
> performance value you should do the following:
> >
> >
> > Compare your most "parallel" algorithm with the performance of a
> corresponding well-written MPI application using openmpi's shared memory
> transport. If there is a difference, then your system has some value.
> >
> > Of course openmpi's shared memory transport is terribly buggy, but it
> should give a baseline acceptable performance.
> >
> > If there is no comparison, we have no idea.
>
> The problem with "implement in MPI and compare" is that you have to
> rearchitect a sequential program for a totally different model.  By
> contrast, using shared memory parallelism, it's often a question of using
> pmap.
>

Incorrect. We always compare to sequential code in parallel computing. It's
called "speedup".

And doubly incorrect because we are not comparing to sequential code but a
claimed shared memory parallelism. It's only logical to compare two
approaches on the same hardware.


>
> I really recommend everybody interested in parallelism to learn and try
> Clojure on a small problem.  You can replace a single map by pmap in a
> suitable setting and observe a not-quite-linear, but proportional speedup.
>

Of course functional programming fits such parallelism very well. It's a
shame that ocaml does not have parallel functional primitives.


>
> I'd be really happy if OCaml gets the mechanisms from Clojure.



It'd be even better if such explicit parallelism had good compiler support,
too :) I don't know much about Clojure, but I wouldn't use anything that
runs on JVM for a parallel program. That might be like first turning your
computer to Commodore 64 and then getting some speedup.


Best,


-- 
Eray Ozkural, PhD candidate.  Comp. Sci. Dept., Bilkent University, Ankara
http://groups.yahoo.com/group/ai-philosophy
http://myspace.com/arizanesil http://myspace.com/malfunct

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