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Re: Converting floor to rint
On Wed, Nov 06, 2002 at 11:29:22PM +0100, Jan Hubicka wrote:
> On the related note. How bad would you consider converting
> floor(x) into rint(x-0.5) in the fast-math mode?
Well, let's see...
If the current rounding mode is FE_UPWARD, then
rint(1.7 - 0.5) = rint(1.2) = 2.0
I.e. we'd be computing CEIL instead of FLOOR.
If the current rounding mode is FE_TONEAREST, which is the case
I assume you were thinking about, we round ties to even, so
rint(5.0 - 0.5) = rint(4.5) = 4.0
instead of the expected value 5.0.
So, I think this would be a very bad idea, even for -ffast-math.