Faster, GHC, and floating point.

[JP Bernardy]

--- ajb at spamcop.net wrote:
> Quoting JP Bernardy <jyp_7 at yahoo.com>:
> 
> > 1. Use -fexcess-precision, unless you really need
> the
> > exact (lesser) precision. Otherwise each
> intermediate
> > result is spilled in memory. This hurts!
> 
> Yes, but it does avoid incorrect numerics, which
> hurts fewer times, but
> when it does, it hurts a LOT more. :-)

With an SSE processor, it is possible to have both
speed and exact precision, passing
-optc-march=pentium4 -optc-mfpmath=sse to ghc, in
addition to -fexcess-precision.

BTW, as requested, I've contributed a page about this
to the haskell wiki. 

http://haskell.org/hawiki/FasterFloatingPointWithGhc

Cheers,
JP.

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