fix composite learning rate (#26227)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26227
In the previous implementation of composite lr, the lr_scale for each sub policy will be rewritten by the last lr_scale.
Due to another bug in unittest (where policy_lr_scale being the same for all sub policies), this bug was not detected by unittest...
Fix: add an additional field in CompositeLearningRateItem so that we store lr_scale values for all sub policies
If fix unittest, the error in previous implementation:
https://fburl.com/testinfra/ikdbnmey
With the fix,
https://fburl.com/testinfra/m694ehl1
Test Plan:
unittest
buck test caffe2/caffe2/python/operator_test:learning_rate_op_test -- test_composite_learning_rate_op
Reviewed By: chocjy, alex1o1o7cloud
Differential Revision: D17380363
fbshipit-source-id: 161e9cb71bb2ea7f0734a3361e270616057a08e4
