On Mon, Sep 25, 2006 at 08:13:50AM -0400, Jacques Carette wrote:
> Over on Haskell-cafe, Simon Peyton-Jones says:
> "GHC 6.6 (release candidate available) supports parallel execution on 
> SMP machines.
> 
> Garbage collection is not parallelised yet, something we plan to fix
> this autumn."
> 
> A bit of competition is a good thing, isn't it?

Can someone explain how/if this is better than using MPI for
parallelism?  The reason I ask is that we are starting to use MPI for
real on SMP machines to process our larger datasets.

On a related note, is/could there be a way in OCaml to tell the GC not
to bother going "into" a particular data structure to check if it part
of it has become unreachable?  Our Weblogs library[1] loads a whole
set of log files into memory (multiple gigabytes of memory), basically
stored in a big linked list with lots of smaller structures hanging
off each element, and I *know* that the hanging elements will never
become unreachable unless the main linked list does so.  I'd like to
be able to tell the runtime that.  Otherwise every time we do a major
collection it's going to be uselessly iterating over the whole lot,
and that appears to have particularly bad consequences as soon as we
start to go into swap.

Rich.

[1] http://merjis.com/developers/weblogs

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Richard Jones, CTO Merjis Ltd.
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