* fix huber_loss ans npair_loss doc and example code, test=document_fix

* remove disable_static in example code, test=document_fix

* remove huber_loss and refine npair_loss example code, test=document_fix

* remove huber_loss in functional/__init__.py, test=document_fix

* migrate code example and doc

functionality provided by `normalize`

* fix typo for interp_v2,test=develop

* align with torch, test=develop

* add area mode, test=develop

* fix bug, test=develop

* format notes, test=develop

* update for converage, test=develop

* fix bilinear, test=develop

* fix bicubic, test=develop

* fix typo, test=develop

* fix coverage, test=develop

* fix helper.input_dtype, test=develop

* polish notes, test=develop

* polish notes, test=develop

* polish notes, test=develop

* add embedding 2.0

* add embedding support input int32

* Add RNN related apis in paddl.nn
test=develop

* new rnn api, cell almost done

* add new progresses in rnn APIs for 2.0

* refine rnn APIs and docstrings.

* add unittets

* disable gpu tests when paddle is not compiled with cuda support

* remove unnecessary imports

* fix docstring

* add to no_sample wlist

* backport to python2 to avoid yield from

* add **kwargs, fix typos

* update docstrings for birnn

* rename argument for SimpleRNN and SimpleRNNCell, fix sample code

* add default value for initial_states in fluid.layers.birnn
Co-authored-by: Nguosheng <guosheng@baidu.com>

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* add norm 2.0 api, test=develop

* api2.0 paddle.nn.Bilinear and paddle.nn.functional.bilinear, test=develop

* api2.0 fix code examples, test=develop

* modify test_bilinear_api, about place,to_tensor , test=develop

* re pass pre-commit, test=develop

* Update common.py

* fix BilinearTensorProduct ci error, test=develop

* add pool2d3d API,test=develop

* add api unitest,test=develop

* fix unittest, test=develop

* fix reviews, test=develop

* return one element when return indices is true, test=develop

* fix low converage; to_variable to to_tensor, test=develop

* sort API params, test=develop

* fix en doc, merge PR#26108 to here, test=develop

* fix en doc, test=develop

This PR enhance CPU kernel and add new CUDA kernel to make grid_sample support:

- align_corners: with bool type.
- padding mode: which can be in ['zeros', 'reflect', 'border']
- Interpolation mode: which ca be in ['bilinear', 'nearest']

The old CPU and CUDNN version only support align_corners=true, padding_mode='zeros' and interpolation_mode='bilinear'.

The behavior of the new version op in default mode is compatible with the old version.

* add alpha_dropout in nn.functional and nn.layer, test=develop

* refine Interface and assertion, test=develop

* fix ci import error, test=develop

* fix alias and use layers.scale, test=develop

* fix doc and training params, test=develop

* refine details in doc, test=develop

* fix doc details, test=develop

* update conv_transpose api

* add binary cross entropy with logit loss

* [API2.0] add dropout, dropout2d and dropout3d, test=develop

* refine Interface and assertion after review, test=develop

* fix alias p=1 and use scale, test=develop

* fix doc and training, test=develop

* fix doc in Dropout2D, test=develop

* add functional ctc_loss and CTCLoss class.

* modified docstring of ctc_loss and CTCLoss

* add adaptive_avg_pool2d

* add adaptive_avg_pool3d

Fix the API of bce loss and add functional API binary_cross_entropy 

* add input.py  file

* write input.py

* fix init file

* add unit tests

* fix dygraph and input shape

* Revert "fix dygraph and input shape"

This reverts commit 89ad8664.

* fixed pylint

* fix deprecated

* fix old op

* fix old op

* set check_dygraph=True

* Revert "set check_dygraph=True"

This reverts commit a8e93e33.

* test commit

* fix doc and change test file name

* add pad func

* add pad

* test=develop, add pad op and apis

* restore pad2d

* test=develop, fix paddl declare

* fix pad interface

* test=develop, fix pad

* test=develop, add all pad api and cos_sim

* test=develop, remove padding default value

* test=develop, rename var to tensor

* test=develop, add more tests

* test=develop, rename tovar to totensor

* test=develop, fix init

* test=develop, add more test

* test=develop, add more tests

add nn.functional.normalize API for API2.0, fix L1Loss API typo, test=develop

* add Class KLDivLoss and function kl_div

add the api and doc for the margin_ranking_loss and MarginRankingLoss

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

fix paddle.nn.loss.L1Loss OP, add paddle.nn.functional.l1_loss OP for API2.0

* add alias in paddle.nn and paddle.tensor test=develop

* add alias in paddle.nn and paddle.tensor dir test=develop

* fix same conflict manually test=develop

* update fc and dygraph alias test=develop

* fix initalizer.py typo test=develop

* define fluid alias in paddle.tensor and paddle.nn dir test=develop

* from layer import loss in paddle.nn dir test=develop