On 2011-12-20 12:48:53 +0100, Dario Saccavino wrote: > In the second program, if 0.5 < f < 1 the values of a and b eventually > become the smallest representable denormal value and never change > afterwards, resulting in a large number of operations involving > denormal numbers. Yes, I agree (I forgot about that)... except that if f is close enough to 1, you won't have subnormals and the program will be fast (like in the case f <= 0.5). > gcc enables FTZ when using SSE and ffast-math (I think the specific > compiler flag is -funsafe-math-optimizations). Thanks, good to know... > Therefore the flags needed are -msse2 -mfpmath=sse -ffast-math I would discourage the use of -ffast-math, which can affect generic code very badly (due to -funsafe-math-optimizations). Isn't there an option to enable FTZ? -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)
