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Date: -- (:)
From: Shivkumar Chandrasekaran <shiv@e...>
Subject: Re: [Caml-list] native threads not parallel?
Not sure if this issue from an earlier discussion was fully resolved or 
not. But I seem to have the same problem as discussed by Markus Mottl 
(see attachment below) on Mac OS X 10.2.4 on a dual processor G4 
machine. An earlier message in that thread mentioned that there was no 
such problem on dual-processor Linux machines.

I have two questions:

1. Has anybody else figured out how to get parallelism using native 
threads on Mac OS X?

2. Will I get the parallelism if I switch to LinuxPPC?

Thanks,

--shiv--

PS: Does ocaml work properly on LinuxPPC?




> Re: [Caml-list] native threads not parallel?
> To :Xavier Leroy < Xavier.Leroy@inria.fr >
> Subject :Re: [Caml-list] native threads not parallel?
> From :Markus Mottl < mottl@miss.wu-wien.ac.at >
> Date: Thu, 21 Jun 2001 15:43:16 +0200
> Cc: OCAML < caml-list@inria.fr >
> Content-Disposition: inline
> In-Reply-To: < 20010615233325.B24915@miss.wu-wien.ac.at >; from 
> mottl@miss.wu-wien.ac.at on Fri, Jun 15, 2001 at 23:33:26 +0200
> References: < 20010615184931.A25835@miss.wu-wien.ac.at > < 
> 20010615191046.A20258@pauillac.inria.fr > < 
> 20010615204218.C25835@miss.wu-wien.ac.at > < 
> 20010615233325.B24915@miss.wu-wien.ac.at >
> User-Agent: Mutt/1.2.5i
> On Fri, 15 Jun 2001, Markus Mottl wrote:
> > I have just been told that things work smoothly with dual-processor
> > machines under Linux, and it also turned out due to more 
> experimentation
> > that the behaviour of native threads under Solaris is comparable to
> > a lottery: when running very long, it seems that multiple threads are
> > used. Sometimes. But sometimes you can also get bus errors. It's 
> really
> > unpredictable. Better don't bother with native threads under 
> Solaris...
>
> I couldn't resist and have done another test now. First, I have made
> sure that multiple threads work under C. As Xavier has pointed out, 
> this
> requires setting the concurrency level to more than the default of 1.
> Works fine (= in parallel).
>
> Then I have written a small test program that tries to do the same 
> under
> OCaml - but no success...
>
> Here are the the timings achieved by calling C via OCaml:
>
>   Running sequentially:
>   Wall clock time: 6.598713
>
>   Running in parallel:
>   Wall clock time: 6.601169
>
>
> Here are the the timings achieved by using C only (clearly runs faster
> with threads):
>
>   Running sequentially
>   Wall clock time: 6.995337
>
>   Running in parallel
>   Wall clock time: 3.910411
>
> The only thing I can imagine is that OCaml somehow changes
> scheduling so that the threads cannot run in parallel anymore, even if
> "enter_blocking_section" is used. Is this possible? Or am I just making
> some stupid mistake?
>
> Regards,
> Markus Mottl

--shiv--

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