BUG: fix corner cases in complex division (were nan+nanj) #26595
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The numpy uses Smith's algorithm to do complex true division. In some
cases (see below) it produces (nan+nanj), but meaningful components
could be recovered. See e.g. C11 Annex G.5.2, _Cdivd()'s example.
>>> 1/complex128('(inf+infj)') # should be 0j
<stdin>:1: RuntimeWarning: invalid value encountered in scalar divide
(nan+nanj)
>>> complex128(inf, -inf)/complex128(1+0j) # should be (inf-infj)
<stdin>:1: RuntimeWarning: invalid value encountered in scalar divide
np.complex128(nan+nanj)
Closes #26560
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Since this touches the inner loops, we should benchmark to make sure any change is acceptable. This will also need a release note. |
It seems I can't built numpy locally (on my old notebook:D), not sure how to do this...
Done. |
In usual case (Smith's division algorithm produces meaningful output) this adds just one extra BTW, here some benchmarks on CPython. Current main, with similar patch: Without: |
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The numpy uses Smith's algorithm to do complex true division. In some cases (see below) it produces (nan+nanj), but meaningful components could be recovered. See e.g. C11 Annex G.5.2, _Cdivd()'s example.
Closes #26560
FYI, related PR in CPython: python/cpython#119457