To add edge_order=2 and documentation for gradient operator (#58165)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/56036
Fixes https://github.com/pytorch/pytorch/issues/56130
* All the interior points are computed using second order accurate central differences method for gradient operator. However, currently we only have first order method computation for edge points. In this PR we are adding second order methods for edge points as well.
* Currently, there is no detailed description of how gradient operator computed using second order method, and how to use parameters correctly. We add detailed explanation of meaning of each parameter, and return of the gradient operator, meanwhile giving description of the second-order computation.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58165
Reviewed By: mruberry
Differential Revision: D29305321
Pulled By: iramazanli
fbshipit-source-id: 0e0e418eed801c8510b8babe2ad3d064479fb4d6
