[Haskell-cafe] Problems with threading?
dons at galois.com
Mon Jun 7 17:50:48 EDT 2010
> While working on the Shootout, I noticed the following benchmarks:
> The same program becomes almost 4 times slower when compiled with --threaded
> and run with +RTS -N5 -- even though the multi-core benchmark really only ever
> uses one processor.
Using -N5 sounds suspicious. There are only 4 cores on the machine.
> Other languages seem to have found a way of arranging these threads in a way
> such that parallelism actually happens, but as it stands, compiling this
> benchmark without --threaded actually makes Haskell competitive against the
> genuinely parallel alternatives in other languages...which is unusual by
> I wanted to throw this out for people to discuss, because I'd like to see it
> improved. As it stands, I'm going to submit a version which asks not to be
> compiled with --threaded (and has a few other improvements).
What parallelization did you try? Is it a good algorithm?
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