On Fri, 27 Apr 2007, Tom Tromey wrote: > Not to be too negative (I am curious about this), but does this sort of > optimization really carry its own weight? Is this a common thing in > numeric code or something like that? > Tom
I don't know that optimizing lgamma by itself makes a big difference. However we're down to the last few C99 math functions and if I can get all of them I think it's worthwhile to be complete. For the record, the remaining ones are lgamma/gamma and drem/remainder/remquo. (Bessel functions have been submitted but not approved yet. Complex math however still needs some TLC.) If you can find something I've overlooked, please let me know. Taken as a whole, I do believe optimizing constant args helps numeric code. E.g. it's noted here that PI is often written as 4*atan(1) and that this idiom appears in several SPEC benchmarks. http://gcc.gnu.org/ml/gcc-patches/2003-05/msg02310.html And of course there are many ways through macros, inlining, templates, and various optimizations that a constant could be propagated into a math function call. When that happens, it is both a size and a speed win to fold it. And in the above PI case, folding atan also allows GCC to fold the mult. --Kaveh -- Kaveh R. Ghazi [EMAIL PROTECTED]
