Re: [Caml-list] Concurrent/parallel programming

[Gabriel Scherer <gabriel.scherer@gmail.com>]

> Also, regarding the ocaml_modify() and ocaml_initialize() regression in 4.01 -- yikes!
> Is there any way to get support back for writing outside of the ocaml heap?
> This seems like a pretty big deal! (Sorry if I'm arriving late for whatever discussion
> took place about this before).

The change was made to improve performances (and indeed gave a nice
boost to modify-heavy code). Labelling it a yikes-worthy regression is
a bit unfair. You should have look at
- the discussion that prompted the change
http://caml.inria.fr/mantis/view.php?id=6019
- the discussion on the ocamlnet problem
http://caml.inria.fr/mantis/view.php?id=6084

Modifying values outside the heap is still allowed using C primitives,
but is not allowed anymore for OCaml heap-update constructs (x.f <-
foo, x.(f) <- foo, etc.).

On Wed, Jan 8, 2014 at 3:35 AM, Yotam Barnoy <yotambarnoy@gmail.com> wrote:
>
> Thanks for the links and info, everyone.
>
> Gerd, would it be possible to put netmulticore up on opam? I realize this is a sensitive topic for you, but from what I can tell, this is the most comprehensive and efficient solution to parallel programming that exists for ocaml, so why not make it as easily available as possible?
>
> Also, regarding the ocaml_modify() and ocaml_initialize() regression in 4.01 -- yikes! Is there any way to get support back for writing outside of the ocaml heap? This seems like a pretty big deal! (Sorry if I'm arriving late for whatever discussion took place about this before).
>
> -Yotam
>
>
> On Tue, Jan 7, 2014 at 3:35 PM, Gerd Stolpmann <info@gerd-stolpmann.de> wrote:
>>
>> There is Netmulticore, a part of Ocamlnet:
>>
>> http://projects.camlcity.org/projects/dl/ocamlnet-3.7.3/doc/html-main/Intro.html#ch_comp
>>
>> It utilizes shared memory, and accesses it from several processes. There
>> is no C code involved, but it is fairly unsafe nevertheless, because you
>> need to stick to certain programming rules, or the program crashes.
>> However, if you manage to encapsulate all the unsafe things, it is a
>> good option. I'm using Netmulticore in the Plasma Map/Reduce
>> implementation.
>>
>> Gerd
>>
>> Am Dienstag, den 07.01.2014, 14:54 -0500 schrieb Yotam Barnoy:
>> > Hi List
>> >
>> >
>> > So far, I've been programming in ocaml using only sequential programs.
>> > In my last project, which was an implementation of a large machine
>> > learning algorithm, I tried to speed up computation using a little bit
>> > of parallelism with ParMap, and it was a complete failure. It's
>> > possible that more time would have yielded better results, but I just
>> > didn't have the time to invest in it given how bad the initial results
>> > were.
>> >
>> >
>> > My question is, what are the options right now as far as parallelism
>> > is concerned? I'm not talking about cooperative multitasking, but
>> > about really taking advantage of multiple cores. I'm well aware of the
>> > runtime lock and I'm ok with message passing between processes or a
>> > shared area in memory, but I'd rather have something more high level
>> > than starting up several processes, creating a named pipe or a socket,
>> > and trying to pass messages through that. Also, I assume that using a
>> > shared area in memory involves some C code? Am I wrong about that?
>> >
>> >
>> > I was expecting Core's Async to fill this role, but realworldocaml is
>> > fuzzy on this topic, apparently preferring to dwell on cooperative
>> > multitasking (which is fine but not what I'm looking for), and I
>> > couldn't find any other documentation that was clearer.
>> >
>> >
>> > Thanks
>> >
>> > Yotam
>> >
>>
>> --
>> ------------------------------------------------------------
>> Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
>> My OCaml site:          http://www.camlcity.org
>> Contact details:        http://www.camlcity.org/contact.html
>> Company homepage:       http://www.gerd-stolpmann.de
>> ------------------------------------------------------------
>
>