On Sat, Apr 5, 2008 at 9:06 AM, NightStrike <nightstrike@xxxxxxxxx> wrote: > Wait, so are things like "c - (c - a)" optimized down to "a" or not? I > use a lot of that in very time-intensive c++ code. > I think only if you tell it to be loose with requirements for applying floating-point math optimizations (-ffast-math and related), since DBL_MAX - (DBL_MAX-1) is, to the best of my knowledge, 0 --- not 1 --- in IEEE math. On the other hand, I managed to get >1 by adding DBL_EPSILON/10 to 1.0 repeatedly (though only on 1 of 4 computers on which I tried it) so my intuitions could all be wrong.
