Anne Archibald wrote: > > Particularly given the comments in the boost source code, I'm leery of > this fix; who knows what an optimizing compiler will do with it?
But the current code *is* wrong: it is not true that u == 1 implies u - 1 == 0 (and that (u-1) != 0 -> u != 1), because the spacing between two consecutive floats is much bigger at 1 than at 0. And the current code relies on this wrong assumption: at least with the correction, we test for what we care about. So I would say the code correction I suggest is at least better in that respect. > Now the > "correction" is completely bogus. I am not sure to understand why ? It is at least not worse than the current code. > Since this is a subtle issue, I vote for delegating it (and log10_1p) > to log1p. If *that* has trouble, well, at least it'll only be on > non-C99 machines, and we can try compiler gymnastics. Yes, we could do that. I note that on glibc, the function called is an intrinsic for log1p (FYL2XP1) if x is sufficiently small. > Clearly the optimizing compiler is inserting the DRDB (drain David's > battery) opcode. :) David _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
