Improve numerical stability of `torch.distributions.wishart.Wishart` (#72993)
Summary:
Maintanance of https://github.com/pytorch/pytorch/pull/70377
Multiple modifications of the merged initial implementation of Wishart distribution.
Key modifications:
* torch/distributions/wishart.py: Clamp (Clip) float type values to calculate reciprocal in numerically stable manner, by using the eps value paired to each torch.dtype
* test/distributions/test_distributions.py: Test Wishart distribution implementation in numerically unstable zones, i.e df values are at ndim - 1 < df < ndim where ndim is the one dimenstion of the Wishart parameter & sample matrix.
Re-opened reverted PR https://github.com/pytorch/pytorch/issues/72059
cc neerajprad vadimkantorov
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72993
Reviewed By: samdow
Differential Revision: D34853807
Pulled By: neerajprad
fbshipit-source-id: eb62dca19bf8a934fdf59b4ffc58587447fe8378
(cherry picked from commit 99240c0d947e2faeb7beae91164ede41f61d8448)
