2016-04-29 16:36 GMT+02:00 Jean-Michaël Celerier < jeanmichael.celer...@gmail.com>:
> > On Fri, Apr 29, 2016 at 1:55 PM, Ola Røer Thorsen <o...@silentwings.no> > wrote: > >> >> float a = 1.0f; >> float b = 2.0*a; // BAD! >> float b = 2.0f*a; // Good! >> > > Pretty sure that this would be a non-problem starting at -O1 optimization > level. > Well you're wrong. If you multiply with a double precision constant value (2.0), the multiplication is done in double precision and the result is then converted to single precision, regardless of the optimize level. This makes a big difference on hardware that only support single-precision in hardware (I know this from experience, not assumptions).
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