* Modified the return value of tensor.grad from numpy as tensor.

* Modify unittests.

* fixed bugs.

* Add warning info for x.grad

* fixed unittests which used x.grad

* fixed bug.

* change prepend to append

* fix ut

* add testcase

* fix ut

* fix test_custom_relu_model

* fix model parallel

* rm parallel_help.py

* add embedding

* support backward return None.

* edit unittest.

* edit code according to CI

* Improve error information

* skip op has no fp16 kernel

* add ut

paddle.to_tensor will be translated to paddle.assign in Dy2stat, however paddle.assign doesn't support int, float, bool. This PR added the supports.

* add pp dygraph, test=develop

* Dygraph reocmpute

* unitest for Dygraph reocmpute

* dy recompute remove unitest for win and mac

* support save/load binary format tensor

* Fix error when create cudaplace

* Fix error when create cudaplace

* Fix error when create cudaplace

* get devive context from pool.

* move define of 'SerializeToStream' and 'DeserializeFromStream' to 'lod_tensor.cc' and 'selected_rows.cc'.

* support complex object

* improve coverage.

* improve coverage

* improve coverage.

* fix a bug.

* polish API

* save/load program

* paddle.save/load: layer

* deal with conflict

* if PY2, block test_paddle_save_load.TestSaveLoadLayer

* polish code.

* polish code

* edit unnittest

* The condition for object to be identified as state_dict becomes strict

* use 'core._cuda_synchronize'

* add pipeline layer

* update

* fix bug: when x.dim < y.dim, the result of compare_op is inverse to expected result

* support the cuda for fix the compare broadcast bug

* fix tc trt shape

* fix fc dynamic shape

* add fc shape assert

* update

* let paddle.utils.install_check support CPU package with GPU device

* use use_cuda in dygraph checking

* add unittest for install_check

Reduce max iter size to fix windows openblas test_yolov3 random failure.
Decrease batch size to fix pe related unittest random failure.

* add c_identity op, test=develop

* refactor_check_finite_and_scale_npu_kernel

* fix compile

* add alloc_float_status op

* add alloc_float_status op

* add FloatStatus for check_finite_and_unscale

* refine code

* remove unneccessary logic

* refine for fleet

* add c_concat op

* fix two error message

* fix two error message

* fix error

* fix error

* fix error

* fix error

* fix some error message

* fix some error

* fix error

* fix some error

* fix some error

* fix some error

* fix one error

* fix some error

* fix seven error message

* fix error

* fix error

* fix error

* fix error

support int32 and int64 kernel for clip operator 

* add clip/check

* add amp & clip grad in dygraph

* add logging

add glu in nn.functional

* support save/load binary format tensor

* Fix error when create cudaplace

* Fix error when create cudaplace

* Fix error when create cudaplace

* get devive context from pool.

* move define of 'SerializeToStream' and 'DeserializeFromStream' to 'lod_tensor.cc' and 'selected_rows.cc'.

* improve coverage.

* improve coverage.

* polish API

* deal with conflict

* disable save/load large file in unnittest

* split unnittest.

* add support for optimizer with varbase input

* refine cond

* fix failed unittest

* add test for coverage

* add paddle.nn.unfold
* update Parameters of Unfold