* add check approval
test=develop

* make fleet_localsgd_meta_optimizer work

* fix bug in localsgd meta optimizer

* set default value to strategy in distributed_optimizer test=develop

set default python3,fix incompatible,cache dir for third party,unify error code,for windows (#26178)

* set default python3 for paddle windows,test=win

* set default python3,cache dir for third party,error code,test=win

* fix some incompatible

* fix some error

* set virtual environment,test=win

* add nll loss API, update demo code of the comment

* upate the target to label, test=develop

* Update the code for the margin_ranking_loss, test=develop

Update the sigmoid, Sigmoid layer for the api2.0

* Fix build whl package

* del timestamp

* fix

* Update `paddle.add`

remove `alpha`
update doc sample code
remove `:alias` etc

* Remove `imperative` reference from docstring

* fix test_multiprocess_dataloader unittest. test=develop

* add children and named_children

* adaptive expand op to 2.0 (align to torch.expand) , test=develop

test=develop

* expose and unify the Tensor concepts to the user

* expose tensor to user

* add copy place for Tensor

* add copy place for Tensor

* add note

* add macro PADDLE_WITH_CUDA

* remove RUN_TYPE=DIST

* fix some error

* add tile_op, test=develop

* add Class KLDivLoss and function kl_div

* show deprecation warning once

* add some notes

* remove unused module

* test=develop, bug fix for test_dist_fleet_ctr

* add paddle.nn.functional.mse_loss

* add name

* fix conflict

* Upgrade `no_grad` decorator

test=develop

- match torch decorator usage (i.e., with parenthesis)
- handle generator functions
- add `paddle.no_grad` alias

* Switch from `functools` to `decorator`

preserves signature

* Reword decorator usage note

* add unittest for paddlerolemaker with gloo

* fix the doc of inverse, dot, cholesky

* fixed static module

* solve conflict

* remove original name for alias API

Update the code for the min,max, test=develop

add the api and doc for the margin_ranking_loss and MarginRankingLoss

* move paddle.fleet to paddle.distributed.fleet

* add auto_cast, test=develop

* add loss scaler, test=develop

* add comments, test=develop

* refine code, test=develop

* refine code, test=develop

* do not set flags automatically, test=develop

* fix custom op bug, test=develop

* add more test, test=develop

* refine enable logic, test=develop

* enable amp test with GPU, test=develop

* add unittest

* add test for found_inf

* follow comments

* follow comments

* remove global variable, use singleton

* add some notes

* update comments

* update comments

* update comments

* add use_dynamic_loss_scaling argument

* refine found_inf

* refine found_inf

* fix loaded var suffix repeat error

* use new dygraph name for loaded param