Implement C++ API torch::nn::MultiMarginLoss. (#27424)
Summary:
Hi yf225 , here is the C++ frontend API MultiMarginLoss implementation and tests https://github.com/pytorch/pytorch/issues/27198. Could you review it and tell me if it is okay?
I am not entirely sure I used `c10::optional` correctly, but `options.weight()` resulted in a compilation error, so I went with `options.weight().value()` instead of `value_or()` to follow the logic in `torch.nn._WeightedLoss.register_buffer` (where one can pass a `None` value).
Oh, and are the tests supposed to be skipped or did I do something wrong? I ran `pytest test/test_cpp_api_parity.py -k Loss -v` , and the `L1Loss` test passed but the others were skipped...
Thank you for the review in any case!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27424
Differential Revision: D17839963
Pulled By: yf225
fbshipit-source-id: f4b6012590cf22d56d42751c214df80cce717cb8
