Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52944
This fix the bug introduced during refactoring optimizers https://github.com/pytorch/pytorch/pull/50411. When all parameters have no grads, we should still allows `beta` like hyper params to be defined.
Reviewed By: ngimel
Differential Revision: D26699827
fbshipit-source-id: 8a7074127704c7a4a1fbc17d48a81e23a649f280
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51316
Make optim functional API be private until we release with beta
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D26213469
fbshipit-source-id: b0fd001a8362ec1c152250bcd57c7205ed893107
Summary:
Adam and AdamW are missing parameter validation for weight_decay. Other optimisers have this check present.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33126
Differential Revision: D19860366
Pulled By: vincentqb
fbshipit-source-id: 286d7dc90e2f4ccf6540638286d2fe17939648fc
Summary:
# What is this?
This is an implementation of the AdamW optimizer as implemented in [the fastai library](803894051b/fastai/callback.py) and as initially introduced in the paper [Decoupled Weight Decay Regularization](https://arxiv.org/abs/1711.05101). It decouples the weight decay regularization step from the optimization step during training.
There have already been several abortive attempts to push this into pytorch in some form or fashion: https://github.com/pytorch/pytorch/pull/17468, https://github.com/pytorch/pytorch/pull/10866, https://github.com/pytorch/pytorch/pull/3740, https://github.com/pytorch/pytorch/pull/4429. Hopefully this one goes through.
# Why is this important?
Via a simple reparameterization, it can be shown that L2 regularization has a weight decay effect in the case of SGD optimization. Because of this, L2 regularization became synonymous with the concept of weight decay. However, it can be shown that the equivalence of L2 regularization and weight decay breaks down for more complex adaptive optimization schemes. It was shown in the paper [Decoupled Weight Decay Regularization](https://arxiv.org/abs/1711.05101) that this is the reason why models trained with SGD achieve better generalization than those trained with Adam. Weight decay is a very effective regularizer. L2 regularization, in and of itself, is much less effective. By explicitly decaying the weights, we can achieve state-of-the-art results while also taking advantage of the quick convergence properties that adaptive optimization schemes have.
# How was this tested?
There were test cases added to `test_optim.py` and I also ran a [little experiment](https://gist.github.com/mjacar/0c9809b96513daff84fe3d9938f08638) to validate that this implementation is equivalent to the fastai implementation.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21250
Differential Revision: D16060339
Pulled By: vincentqb
fbshipit-source-id: ded7cc9cfd3fde81f655b9ffb3e3d6b3543a4709
