[Numpy-discussion] Recent work for branch cuts / C99 complex maths: problems on mingw

Pauli Virtanen pav@iki...
Tue Jul 29 09:38:15 CDT 2008


Tue, 29 Jul 2008 08:13:23 -0600, Charles R Harris wrote:
[clip]
> We also need speed. I think we just say behaviour on the branch cuts is
> undefined, which is numerically true in any case, and try to get the
> nan's and infs sorted out. But only if the costs are reasonable.

Well, the branch cut tests have succeeded on all platforms so far, which 
means the behavior is numerically well-defined. I doubt we can lose any 
speed by fixing sqrt in this respect.

The inf-nan business is the one causing problems. Lookup tables might 
solve the problem, but they add a few branches to the code even if the 
arguments are finite.

-- 
Pauli Virtanen



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