Floating point performance issue

Vincent Lefevre vincent+gcc@vinc17.org
Tue Dec 20 13:02:00 GMT 2011

On 2011-12-20 13:30:30 +0100, Segher Boessenkool wrote:
> Dunno about that(*), but you can portably do
> fesetround(FE_TOWARDZERO);
> and that prevents the problem from occurring as well.

But this is a bad idea in general, as it would affect all FP operations,
not just subnormals (when one gets subnormals, one has already lost much
precision, so that FTZ may not be a problem in practice -- this depends
on the application, of course).

Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)

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