[Haskell] Implicit parallel functional programming
Keean Schupke
k.schupke at imperial.ac.uk
Thu Jan 20 03:42:34 EST 2005
Ben Lippmeier wrote:
>
> I thought the "lazy functional languages are great for implicit
> parallelism" thing died out some time ago - at least as far as running
> the programs on conventional hardware is concerned.
>
> Designing an algorithm that breaks apart a "sequential" lazy program
> into parallel chunks of the appropriate size is **HARD** (with double
> asterixes). The time and space behavior of a lazy program is complex
> enough for the _programmer_ to reason about, let alone an automated
> analysis - which has no knowledge of what the program is actually
> trying to do.
>
I guess this is true, but only if you are trying to find the optimal
solution (or prooveably optimal
solution)... There must me many ad-hoc solutions with reasonable
performance. Perhaps a good first step would be a solution bounded in
the worst case by the sequential execution time (IE the multi-CPU
version would be no slower than the single CPU version, excluding the
locking overhead). If something were to win on 2/4/8 cpu machines most
of the time I think it would
be useful.
Keean.
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