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

[Lucas Dixon <ldixon@inf.ed.ac.uk>]

On 13/04/2011 09:01, Gerd Stolpmann wrote:
> Am Dienstag, den 12.04.2011, 23:36 -0400 schrieb Lucas Dixon:
>> On 24/03/2011 19:13, Fabrice Le Fessant wrote:
>>> On 03/24/2011 02:45 PM, Alexy Khrabrov wrote:
>>>>> Where does the OCaml team stand on the multicore issues?  A year
>>>>> or so ago, when there was a prototype parallel GC implementation,
>>>>> IIRC, Xavier said it has to be done right.  So what are the
>>>>> official plans and the status of integrating what volunteers had
>>>>> done?
>>>>>
>>>>> WIth Scala having a robust actors model and AKKA kernel, and
>>>>> Clojure built around efficient shared memory concurrency with
>>>>> agents and references and STM, and Haskell also really parallel,
>>>>> OCaml is lacking behind.  Furthermore, F# builds on strongly
>>>>> parallel .NET, overcoming granddaddy.  With multicores common
>>>>> even in laptops and iPads, we need an efficient  multicore OCaml!
>>>>> Due to the model different from Haskell or Scala and Clojure, now
>>>>> all on github, OCaml is both more stable and also is slower to
>>>>> advance -- what do folks think about this situation?  How do you
>>>>> do shared memory parallelism now?
>>>>>
>>>>> Cheers, Alexy
>>>>>
>>
>> The PolyML implementation of SML has had a multi-core runtime, without
>> slowing down single-threaded programs for a few years now.
>
> How do you know that there are no slow-downs? Has it ever been tried to
> get rid of all additional measures that are necessary to support
> multicore? There might be e.g. architectural simplifications that would
> lead to speed-ups for the single-threaded case.

Before it was introduced, PolyML was single-threaded. We compared 
running on the single-thread version of PolyML against using a single 
thread in the multi-threaded version. It may be that some optimisations 
were also introduced that cancelled out a slowdown from the 
multi-threaded version, but I can't remember anyone mentioning this.

best,
lucas

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