* support bf16 in AmpOptimWrapper

* add docstring

* modify docs

* add unittests for bf16 in AmpOptimWrapper

* fix type

* fix to pass ci

* fix ut skip logic to pass ci

* fix as comment

* add type hints

* fix docstring and add warning information

* remove check for pytorch>=1.6 in unittest

* modify unittest

* modify unittest

* remove torch.float32 && torch.float64 from valid dtypes

* fix as comments

* minor refine docstring

* fix unittest parameterized to pass CI

* fix unittest && add back torch.float32, torch.float64

* add ApexOptimWrapper

* typo fix

* add apex amp.initialize in optim_context

* assert apex_amp

* polish code

* add parameters of apex_amp.initialize

* add docs

* polish code

* polish code

* polish code

* fix calling of apex amp load_state_dict

* polish

* add comments

* Update apex_optimizer_wrapper.py

* Update apex_optimizer_wrapper.py

---------

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

* [Enhance] add documents for , and support clip grad by value

* refine docstring

* fix as comment

* Fix as comment

* minor refine

* minor refine

* remove error comment for clip grad

* refine docstring

* fix merge ci

* make timeout larger

* tmp test merge

* debug

* sleep 1 in optimizer ut

* skip test clip grad

* skip test clip grad

* fix merge ci

* Rename data to structure

* adjust the way to import module

* adjust the way to import module

* rename Structure to Data Structures in docs api

* rename structure to structures

* support using some modules of mmengine without torch

* fix circleci config

* fix circleci config

* fix registry ut

* minor fix

* move init method from model/utils to model/weight_init.py

* move init method from model/utils to model/weight_init.py

* move sync_bn to model

* move functions depending on torch to dl_utils

* format import

* fix logging ut

* add weight init in model/__init__.py

* move get_config and get_model to mmengine/hub

* move log_processor.py to mmengine/runner

* fix ut

* Add TimeCounter in dl_utils/__init__.py

* [Refactor] Refactor the import rule

* minor refinement

* add a comment

* fix save scheduler state dict with optim wrapper

* remove for loop and inherit TestParameterScheduler

* remove for loop and inherit TestParameterScheduler

* minor refine

* fix optimizer wrapper counts

* fix ut

* merge context

* update unit test

* add docstring

* fix bug in AmpOptimWrapper

* add docstring for backward

* add warning and docstring for accumuate gradient

* fix docstring

* fix docstring

* add params_group method

* fix as comment

* fix as comment

* make default_value of loss_scale to dynamic

* Fix docstring

* decouple should update and should no sync

* rename attribute in OptimWrapper

* fix docstring

* fix comment

* fix comment

* fix as comment

* fix as comment and add unit test

* Support multiple optimizers

* minor refinement

* improve unit tests

* minor fix

* Update unit tests for resuming or saving ckpt for multiple optimizers

* refine docstring

* refine docstring

* fix typo

* update docstring

* refactor the logic to build multiple optimizers

* resolve comments

* ParamSchedulers spports multiple optimizers

* add optimizer_wrapper

* fix comment and docstirng

* fix unit test

* add unit test

* refine docstring

* RuntimeInfoHook supports printing multi learning rates

* resolve comments

* add optimizer_wrapper

* fix mypy

* fix lint

* fix OptimizerWrapperDict docstring and add unit test

* rename OptimizerWrapper to OptimWrapper, OptimWrapperDict inherit OptimWrapper, and fix as comment

* Fix AmpOptimizerWrapper

* rename build_optmizer_wrapper to build_optim_wrapper

* refine optimizer wrapper

* fix AmpOptimWrapper.step, docstring

* resolve confict

* rename DefaultOptimConstructor

* fix as comment

* rename clig grad auguments

* refactor optim_wrapper config

* fix docstring of DefaultOptimWrapperConstructor

fix docstring of DefaultOptimWrapperConstructor

* add get_lr method to OptimWrapper and OptimWrapperDict

* skip some amp unit test

* fix unit test

* fix get_lr, get_momentum docstring

* refactor get_lr, get_momentum, fix as comment

* fix error message

Co-authored-by: zhouzaida <zhouzaida@163.com>