* update build_once for cycle_gan
test=develop

* add input_channel arg
 for cycle_gan
test=develop

test=develop

test=develop

* modify senta dygraph

* modify details

* update ptb model to use auto generated op functions, test=develop

* refine model code, test=develop

* refine model code, test=develop

* update ptb model, test=develop

test=develop

test=develop

* update ptb model to use auto generated op functions, test=develop

* refine model code, test=develop

* refine model code, test=develop

* add gru and bigru net

* add gru and bigru

* add gru and bigru

* Use new save/load api and change fluid.layers.data to fluid.data (#3547)

* Use new save/load api and change fluid.layers.data to fluid.data

* add check for paddle version

* Use new save/load api in ptb_lm (#3546)

* Use new save/load api in ptb_lm

* add check for paddle version

* unify reader to dataloader (#3488)

unify reader to dataloader

* Use new save/load api and change fluid.layers.data to fluid.data (#3547)

* Use new save/load api and change fluid.layers.data to fluid.data

* add check for paddle version

* Add beam search for dygraph Transformer.
Re-organize dygraph Transformer.

* Add custumed data support for dygraph Transformer.

* Add validation in dygraph Transformer.

* Update notes for multi-gpu for dygraph Transformer.

* user new save load in all dygraph modell; test=develop

* change load_dict to set_dict; test=develop

* using new load api

* merge

* add dygraph user guide in models/dygraph

* remove useless files

* fix model save

* fix doc

* update gan model

* update gan model time display

* update gan script

* update gan script

* using new load api

* fix transformer crashed when dropout seed get None

* fix ptb reader and remove useless language model; test=develop

* add ptb reader; test=develop

* using new load api

* test=develop, add license

add copyright for cycle_gan and se_resnext

* fix ptb author bug; test=develop

* fix ptb author bug; test=develop

fix ceroot path bug

* Update mnist_dygraph.py

fix bug

* add muti card support for se_resnext

* add some description to readme.md

* add ce for cyclegan

* fix code style

* add ce for ptb_lm

* Update mnist_dygraph.py

fix bug

* add ce to se_resnext

* delete useless comments and fix unique_name bugs

* add sentiment ce

* delete some comment

* fix code style

* Update mnist_dygraph.py

fix bug

* add muti card support for se_resnext

* add some description to readme.md

Update mnist_dygraph.py
fix bug
* add ce to se_resnext
* delete useless comments and fix unique_name bugs

* fix typo

* fix reademe

* fix init_path for test

* add se_resnext for dygraph

* add ce for dygraph mnist

* add ce for dygraph mnist

* del mnist_dygraph.py

* change mnist_dygraph to train

* fix print style

* add resnet

* fix ce bug

* fix ce decsription

* add ce for dygraph mnist

* add ce for dygraph mnist

* del mnist_dygraph.py

* change mnist_dygraph to train

* fix print style

* add multi process reader

* use distributed_batch_reader

load_persistables function returns a tuple which include parameters and optimizer

1.Modify the checkpoint save path
2. Modifiy the img save paht
3. Synchronous modification for Readme
4. update generated result img

fix load bug

Symbol Modification