remove unused vars which block the build

Recv OP: use BlockDesc* instread of ProgramDesc proto as Attribute

Fix the description of default scale attribute for scale op.

Add distribution implement of image classification

Add python wrapper for sequence reshape operator.

Add sequence reshape operator

* check if kernel if found for kernel type

* do kernel check before data transform

Change input data type to int64_t

* add data layout transform and optimize the implementation of data_transform

* add new_op_kernel_en.md

Add CTC align op

delete memory copy from linear_chain_crf_op.

Enhance GPU kernel of sequence erase op 

Add python doc for dynamic_lstm

* update new_op doc

* follow comment

Make merge and split support lodtensor

bring back test_parallel_do 

update doc and dist test due to transpiler change

Enhance distributed train performance

make auto-registry layers supporting specified output

* add split selected rows op

* update comment

* add grad check

* registry cuda kernel

* fix ci failed

Fix compiling warnings

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into distributed_split_selectedrows

update doc and dist test due to API change https://github.com/PaddlePaddle/Paddle/pull/7619#pullrequestreview-89656079

Remove optimize_op argument from get_pserver_program method of Distributed Transpiler

doc update with #7667