Documentation LU Decomposition: deriving L, U, and P (#36907)
Summary:
Add note to LU decomposition to use `lu_unpack` to get `L`, `U`, and `P`.
Fixes https://github.com/pytorch/pytorch/issues/36752.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36907
Differential Revision: D21134545
Pulled By: albanD
fbshipit-source-id: 54d4872bb8c95dfb8048aedace9781f843ab8a30
