pytorch

1321f2bf - [PyTorch] Port Caffe2 opti for BatchMatMul batch size 1 to baddbmm (#51057)

[PyTorch] Port Caffe2 opti for BatchMatMul batch size 1 to baddbmm (#51057) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/51057 Caffe2 has an [optimization](https://github.com/pytorch/pytorch/blob/f8eefbdf7a229abbb864e47e0b664c7628d80224/caffe2/operators/batch_matmul_op.h#L192) for the case where the batch size is 1 that uses the underlying `gemm` instead of `gemm_batched` BLAS function. This diff tries to port that optimization to `baddbmm_mkl`. Note that I have very little linear algebra background and am just going off existing code and cblas API documentation, so please review without assuming I know what I'm doing with the math itself. ghstack-source-id: 120342923 Reviewed By: hlu1 Differential Revision: D26056613 fbshipit-source-id: feef80344b96601fc2bd0a2e8c8f6b57510d7856