Peter Jay Salzman writes: > The man page claims that "-ffast-math" may produce wrong results for > programs that depend on "an exact implementation of IEEE or ISO > rules/specifications for math functions." > > What exactly does this vague sentence mean? The main problem is that Infs and NaNs are manipulated as finite numbers in optimisations and comparisons with -ffast-math. e.g. you can find that x-x==0 for x=Inf and other similar oddities. Some programs use non-standard idioms like if(x!=x) for checking if x is NaN. -- Brian Gough (GNU Scientific Library Maintainer) p.s. don't forget to profile your program. Network Theory Ltd, Publishing "An Introduction to GCC" --- http://www.network-theory.co.uk/gcc/
