Added pow() on CPU for float16 & bfloat16 (#50999)
Summary:
Added the functionality desired in https://github.com/pytorch/pytorch/issues/50789.
1. Added support for pow() on CPU for `float16` (`Half`) and `bfloat16` types.
Both `pow(Tensor, Scalar)` and `pow(Tensor, Tensor)` are now supported for the aforementioned types.
However autograd isn't supported for `Float16` on CPU yet, as `log_vml_cpu` can't be enabled for it.
2. heitorschueroff added `pow_tensor_scalar_optimized_kernel` to refactor & simplify `PowKernel.cpp`.
It provides a common path for all the complex types & floating point types (except Float16, due to lack of complete AVX2 vectorization support for it). It replaced code that had previously been duplicated for (float, double) and complex types,
so PowKernel.cpp looks a lot cleaner now.
3. Enabled (unskipped) some tests for `erf`, `erfc`,`erfinv`, `linalg.norm` and `linalg.vector.norm` which were being skipped earlier due to `pow()` not having been implemented for `float16` & `bfloat16`.
4. Added an OpInfo for `pow()` & enabled some test cases for `pow()`.
5. Extended the coverage of existing tests for `pow` in `test_binary_ufuncs.py` in order to enable comparison with `numpy`, even with discontiguous tensors, and added a test to ensure that a runtime error is raised for `pow`'s inplace variant if resizing the base tensor is required during its invocation.
6. Added `float16` & `bfloat16` to `square`'s dtype lists in its `UnaryUfuncInfo`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50999
Reviewed By: zou3519
Differential Revision: D27478225
Pulled By: heitorschueroff
fbshipit-source-id: d309dd98d5a96d0cb9b08281757bb1c65266d011
