Implements complex isfinite and isinf (#36648)
Summary:
Implements complex isfinite and isinf, consistent with NumPy.
A complex value is finite if and only if both its real and imaginary part are finite.
A complex value is infinite if and only if its real or imaginary part are infinite.
Old isfinite, isinf, and isnan tests are modernized and instead of fixtures the torch results are compared with NumPy. A new test is added for complex isfinite, isinf, and isnan. The docs for each function are updated to clarify what finite, infinite, and NaN values are.
The new tests rely on a new helper, _np_compare, that we'll likely want to generalize in the near future and use in more tests.
Addresses part of the complex support tasks. See https://github.com/pytorch/pytorch/issues/33152.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36648
Differential Revision: D21054766
Pulled By: mruberry
fbshipit-source-id: d947707c5437385775c82f4e6c722349ca5a2174
