[Haskell-cafe] Re: Haskell version of ray tracer code is much slower than the original ML

Philip Armstrong wrote:

On Thu, Jun 21, 2007 at 08:15:36PM +0200, peterv wrote:

...

So float math in *slower* than double math in Haskell? That is interesting. Why is that?

BTW, does Haskell support 80-bit "long double"s? The Intel CPU seems to use that format internally.

As I understand things, that is the effect of using -fexcess-precision.

Obviously this means that the behaviour of your program can change with seemingly trivial code rearrangements,

Not just code rearrangements: your program will give different results depending on the optimisation settings, whether you compile with -fvia-C or -fasm, and the results will be different from those on a machine using fixed 32-bit or 64-bit precision floating point operations. Cheers, Simon