* 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 SyncBatchNorm,test=develop

* logsigmoid and LogSigmoid, test=develop

* add elu gelu relu, test=develop

* update to_variable to to_tensor, test=develop

* address review comments, test=develop

* address review comments, test=develop

* change to_variable to to_tensor in test, test=develop

* add Class KLDivLoss and function kl_div

add the api and doc for the margin_ranking_loss and MarginRankingLoss

add pairewise distance for the paddlepaddle api 2.0

* add Pad2D and Leaky_ReLU, test=develop

* update,test=develop

* change name,test=develop

* add unittest and redine docs,test=develop

* 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

* add base name alias; test=develop

* fix embedding bug; test=develop

* fix io error; test=develop

* add metric; test=develop

* add import palce; test=develop

* add setup; test=develop

* fix incubate reader; test=develop

* fix initializer error; test=develop

* test=develop add linear interpolate operator

* copy dygraph api to paddle.imperative, test=develop

* polish the code, test=develop

* polish code, test=develop

* polish code, test=develop

* move paddle.imperative.Layer to paddle.nn.Layer, test=develop

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

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

* add diag_embed op, test=develop

* add TestCase of diag_embed API

* Modified diag embed python API teastcase from dygraph to static graph, test=develop

* delete useless log and trigger ci, test=develop

* modified float16 of diag_embed, test=develop

* modified en doc of diag_embed

* trigger ci, test=develop

* add fp16 in dtype check of python API, test=develop

* modified __init__ and fix a big, test=develop

* modified a test bug of test_bicubic_interp_op and test_trilinear_interp_op, test=develop

* modified to use one kernel on cpu and cuda, test=develop

* add nll_loss op test=develop

* add approximation for gelu, test=develop

* add functional conv

* add test and doc for function convs, test=develop

* update ConvTransposeOp's InferShape and error message, test=develop

* add hsigmoid, row_conv in paddle.nn(functional and layer), test=develop

* fix hyperlinks in docstring

* add cross_entropy_loss,test=develop
* fix some commnet,test=develop

* add bce_loss

* fix mistake

* replace paddle_enforce,test=develop

* fix,test=develop

* update,test=develop

* remove duplicate,test=develop

* update,test=develop

* update error,test=develop

* update,test=develop

* fix unittest, test=develop

* update, test=develop

* add instance_norm op for dygraph, test=develop

* add error message, test=develop

* add Conv/ConvTranspose layers in paddle.nn.layer, test=develop

* add example code in docstring, test=develop

* update unittests to work with test_runner, test=develop

* add functional conv

* add test and doc for function convs, test=develop

* update ConvTransposeOp's InferShape and error message, test=develop

* add L1Loss

* support L1Loss, test=develop

* add test, test=develop

* fix batch, test=develop

* follow comments, test=develop

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

* define alias in paddle.nn.functional dir test=develop

* define alias in paddle.tensor.__init__.py test=develop

* fix high level API(Inference) bug

* patch the unit tests

* Use for_test=True in the Fluid Trainer to clone the test program

* fix typo

* Should do the samething to the inferencer

* add Inference.infer

* optimize code

* update no_test_word2vec_new_api.py

* update trainer

* split check_and_get_place

* use inference_program to save inference model in Trainer

* update demo

* update save_inference_model

* clean code