* Update crf_decoding api & example

test=develop

* Update api spec

test=develop

* Fix linear chain crf api

test=develop

* Avoid sharing data pointer with input

test=develop

* Simplify the logic in linear_chain_crf_decoding

* Add unittest for crf_decoding when label & path both are set

test=develop

* Update API spec

test=develop

* Add unittest for layers && correct infer_shape in chunk_eval

test=develop

* fix the error message for reduce_mean and reduce_sum op test=develop

* fix typo test=develop

* fix according review advice test=develop

* fix the test test=develop

* fix test=develop

1.support asymmetric padding;
    2.support padding algorithm:"SAME" and "VALID";
    3.support channel_last: data_format NHWC and NDHWC;
    4.change doc of python API and c++;

    test=develop, test=document_preview

* refine doc, test=document_fix

* add API.spec,test=develop,test=document_fix

* test=develop, argument shape support tensor and tensor in list

* test=develop,Increasing the coverage of CI tests

* test=develop, modify the document and update API.spec

* test=develop, modify the doc and update API.spec

* test=develop, modify the doc and update API.spec

* test=develop, modify the interface of UniformInitializer

* test=develop, modify the interface of XavierInitializer and MSRAInitializer

* test=develop, modify based on review's comments

* test=develop, modify based on review's comments

*  test=develop, modify based on review's comments

* fix pool2d pool3d:
1. support asymmetric padding;
2. support padding algorithm:"SAME" and "VALID";
3. support channel_last: data_format NHWC and NDHWC;
4. support inferring shape when input with negative dims in compile time;
5. change doc of python API and c++;
6. fix bug in cuda kernel when Attr(adaptive) is true.

test=develop,test=document_preview

* fix 'tensors' to 'Tensors'. test=develop,test=document_preview

* add test for converage ValueError.test=develop,test=document_preview

* resolve conflict in test_pool2d. test=develop

* fix en docs of apis, test=develop, test=document_fix

* follow chunwei's comments, test=develop

Polish English docs of elementwise_add/sub/mul/div

Polish elementwise max min pow document to add more examples

* refine doc, test=develop, test=document_preview

* add support tensor and tensorlist for strided_slice OP test=develop

* fix the commnet test=develop

* fix test=develop

* fix the bug test=develop

* delete log test=develop

* fix API.spec test=develop

* fix test=develop

* update API.spec

* refine ctc align op with padding 
* refine api sample code

* add input type and dtype check for softmax_op

test=develop

* refine error message

test=develop

* Removing last dims constraints of seq_pad and seq_unpad test=develop

* fix test_layer api code test=develop

* fix sequence_pad_op.cc conflict test=develop

* remove test_analyzer_mm_dnn test=develop

* fix vectorize bug test=develop

* fix vectorize<int> test=develop

test=develop
test=document_fix

* add mse_loss op

* move tree_conv to fluid.contrib.layers

test=develop

* update API.spec for tree_conv

test=develop

* update tree_conv api to increase unit coverage

test=develop

* add instance norm op

* refactor dygraph,test=develop

* fix failed unittest,test=develop

* polish code,test=develop

* check windows ci error,test=develop
try to fix windows ci error by np.allclose,test=develop

* polish vlog and profiler, test=develop

* try to fix preceding ops order,test=develop

* test transformer in windows ci, test=develop

* use python c-api to speed up tracer.trace,test=develop

* test=develop, fix docker with paddle nccl problem

* test=develop, add ut for debug string and gradient_accumulator

* test=develop, add tests for layer/gradient_accumulator/prepared_op

* test=develop, fix complie error for test_prepared_op

* test=develop, add more ut for dygraph

* test=develop, create API.spec for dygraph api change

* test=develop, refoctor name to make it easier to understand

* test=develop, refoctor name to make it easier to understand

* test=develop, fix multi-gpu failed problem , add Tracer tests, change PADDLEENFORCE to PADDLEENFORCE_EQ

* test=develop, fix ut failed on parallel se-resnext

* test=develop, change one more PADDLE_ENFORCE

* support auto prune in dygraph mode

* test=develop, support auto prune

* test=develop, merge develop conflict

* test=develop, fix test_layer and test_tracer ut

* test=develop, fix bug which may cause stop_gradient disabled with a list of backward inputs

1. group_norm support data_layout=NHWC
2. modified doc of group_norm

modified interpolate_op to support tensor attribute

1. the parameter out_shape of image_resize、resize_nearest/bilinear/trilinear can be a list or a 1-D tensor variable. If a list, each element can be an integer or a tensor variable with shape: [1].

2. the parameter scale of above Ops can be a 1-D tensor variable.
modified document of image_resize, resize_nearest, resize_bilinear, resize_trilinear and add some code example.

add crop_tensor op. The main difference with crop is :

1. If the argument shape is a list, each element is an integer or a tensor variable with shape: [1]. This way is suitable for the case that the shape may be changed each iteration.

2. If the argument shape is a variable. Its rank must be 1. In crop op, the rank of shape must be the same as x

offsets can be a list, in which each element is an integer or a tensor variavle with shape: [1].

* add precise roi pooling op test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* detail the description test=develop

* test=develop

* elaborate the doc for return type test=develop

* test=develop

* strided_slice op basic function test=develop

* test=develop rewrite and fix

* fix bug test=develop

* fix for the PADDLE_ENFORCE usage

* add some unit testw

* fix for the aip  test and copright and fix test=develop

* fix API.spec test=develop

* fix API.spec test=develop

* add axis parameter test=develop

* fix for the build error test=develop

* fix python api  test=develop

* fix the build test=develop

* fix build test=develop

* fix API spec test=develop

* test=develop add some comment and single op test

* fix API spece test=develop

* fix test=develop

* fix test=develop

* fix api test=develop

* fix api test=develop

* fix API.spec test=develop

* fix typo test=develop

* fix API.spec test=develop

* fix API typo test=develop

* fix doc and API.spec test=develop

* add deformable conv v1 op, test=develop

improve pow op according to reviews:
1. Delete unnecessary judgement statements in PowGradOpDescMaker;
2. Improve test of test_api;

overload GetKernelTypeForVar

add stop_gradient=True when attr(factor) is tensor Variable, change examples in API pow.
test=develop,test=document_preview

add support parameter inference when argument shape is a list containing integer and tensor variable;
test=develop

fix reshape op according to reviews:
1. improve or message;
2. improve test of test_api.
test=develop,test=document_preview

fix reshape op: Add error message in nn.py, test=develop

add stop_gradient=True when attr(shape) is tensor Variable.
change examples in API reshape.
test=develop,test=document_preview

add support parameter inference when arguments starts or ends is a list containing integer and tensor variable;
test=develop,test=document_preview

improve slice op according to review(from hongyu). test=develop

fix slice op according to review: infer_flags, test=develop

fix slice op: improve overload operator __getitem__ to support attrs(starts and ends) are Variable.
test=develop,test=document_preview

fix test_slice_op: add TestSliceOp_decs_dim_6 to resolve conflict with test_slice_ngraph_op. test=develop

add stop_gradient=True when attr(starts) or attr(ends) is tensor Variable.
test=develop,test=document_preview

1. add tensor support for argument expand_times in expand op;
2. add support parameter inference when argument expand_times is a list containing integer and tensor variable;

improve expand op according to reviews:
1. add doc of ExpandTimes in expand_op.cc;
2. improve the test of test_api.

add stop_gradient=True when attr(expand_times) is tensor Variable, change code examples.
test=develop,test=document_preview

remove unused accuracy-diff warpctc-cudnn implementation

test=develop

* delete args on linear_chain_crf_op doc

* delete args on linear_chain_crf_op doc

* delete args on linear_chain_crf_op doc

* add code example

* fix api doc

* fix doc of crf

* fix doc of crf

* add test=develop

* modify API.spec, test=develop

* delete useless raw variables in Conv2D, test=develop

* adjust the vars number in test_graph_wrapper to pass unittest, test=develop

* add scatter_nd op, test=document_preview test=develop

* fixed the document, test=document_preview test=develop

* modify the notes, test=document_preview test=develop

* remove the ShareDataWith, test=develop

* add padding in linear_chain_crf op

* modify API.spec

* add linear_chain_crf_op.cc and linear_chain_crf_op.h

* remove useless unit test , test=develop

* modify API.spec, test=develop

* remove some blanks in nn.py , test=develop

* fix some bugs on nn.py and API.spec ,test=develop

* fix nn.py, test=develop

* fix API.spec ,test=develop

* fix bug of CI test in test_linear_chain_crf_op.py

* fix bug of CI test in test_linear_chain_crf_op.py, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* modify nn.py, test=develop

* fix API.spec, test=develop

* fix unittest bug, test=develop

* Support looking up embeddings from BoxPS.
* Add a _pull_box_sparse op, for now this op is not exposed to users.
* Add a BoxHelper class, providing 'BeginPass', 'EndPass', 'FeedPass' functions and so on.
* Add 'BoxPSDataset' in python code.
* Add a compile options WITH_BOX_PS and a MACRO PADDLE_WITH_BOX_PS.
* Add UT.
* More concrete information pls refer to: https://github.com/PaddlePaddle/Paddle/pull/18982

* fixed the code for coverage

* fixed the document,test=document_preview test=develop

* add topk_avg_pooling

* refine api doc and modify api.spec test=develop