Refactor cub namespace handling (#66219)
Summary:
This PR is to update PyTorch with the following cub changes:
- Starting cub 1.13.1, cub requires users to define `CUB_NS_QUALIFIER` if `CUB_NS_PREFIX` is also defined. Besides that, a new mechanism `CUB_WRAPPED_NAMESPACE` is added.
And I do the following change to PyTorch:
- Starting CUDA 11.5, define `CUB_WRAPPED_NAMESPACE` globally as an nvcc flag.
- Fix caffe2 failures caused by the above change.
- Add a `aten/src/ATen/cuda/cub_definitions.cuh` that defines helper macros about feature availability.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66219
Reviewed By: bdhirsh
Differential Revision: D31626931
Pulled By: ngimel
fbshipit-source-id: 97ebf5ef671ade8bf46d0860edc317f22660f26d
