* Add new API: paddle.prod

test=develop

* verify correctness of dy2static model by using paddle-inference api

* update python doc style

* disable UT temp

* add print test_dist UT elapsed time

* UT elapsed time optimize

* Rename `Input` into `InputSpec`

* remove alias

* add weight_norm, test=develop

* fix the doc of dot

(1) Add api paddle.reshape(x, shape, name); 

(2) Use Tensor replaces Variable. test=develop

* add save/load for parameter server

* Rename `Input` into `InputSpec`

* fix argument place of Input api

* enhance add parameter check for layer

* add unittest for coverage

* remove uninit test case

* enrich unittest ccase

* trigger ci check

* 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

* rename input

* add unittest, test=develop

* use paddle.data instead of fluid.data, test=develop

* 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

* reduce the execution time of affine_channel op unittests

* support ps-gpu

* add zero norm, inf norm support for p_norm op

* fix the invalid argument check, fix the dtype problem in test case.

* 1.Fix api sum:(1) input->sum; (2)dim->axis; (3)keep_dim->keepdim.

* 2. fix bug when len(axis) == len(x.shape). 

* add Sampler/SequenceSampler/RandomSampler. test=develop

* 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 check if fluid.data() variable no feed data, test=develop

* Add testcase for feed check, test=develop

* Conv2d_transpose and mul support channnelwise quantization, test=develop
* Skip collecting out threshold for output tensor of which the type is not fp32 or fp64, test=develop
* Fix error in test_user_defined_quantization, test=develop
* Add depthwise_conv_bn_fuse, test=develop
* Add conv_transpose_bn_fuse_pass for post_training_quant, test=develop

align expand_as op to expand.