* test=develop, communicator_is_sgd_optimizer flags

* add check nan / inf in downpour worker during training
* test=develop

* fix fetch handler error with pslib
* fix distributed lookup table op with 1 pserver

* move pool2d to add_quant_dequant_pass, test=develop

* fix elementwise_floordiv_op and elementwise_mod_op, test=develop

* fix API.spec, test=develop

* fix API.spec, test=develop

test=develop

* Support fp16 in fused_elemwise_activation_op.
* Fix unit testing in ONLY-CPU mode.

* refine error message of input TypeError in framework.py

test=develop

* refine error message

test=develop

* update test_compare_op.py unit-test to improve coverage

test=develop

* test=develop,Fix communicator slow bug

* test=develop, delete if() in stop_worker()

* test=develop

* fix UT, test=develop

* fix bug in fetch handler, test=develop

* fix bug in fetch handler, test=develop

* test=develop, fix fetch barrier bug

* test=develop, bug fix

* test=develop, bug fix

* test=develop, fix bug

* bug fix: invalid learning rate decay in pserver async mode

* fix error message for elementwise_add/mul;test=develop

* fix type error message;test=develop

* add data type check, test=develop

* polish error messages, test=develop

* polish error messages, test=develop

* Remove support for the CPU architecture matmul, test=develop

* fix syntax bug, test=develop

* special case: strategy is None

* add input type and dtype check for cast_op
test=develop

* fix annotation
test=develop

* support more data type

test=develop

* fix bug for fill_constant's error type

test=develop

* improve converage

test=develop

* improve converage

test=develop

* fix api fluid.cuda_pinned_places, test=develop

* fix api fluid.cuda_pinned_places, test=develop

* support dump multi file
test=develop

* dump fix num file
test=develop

 Add detail logs on resnet unit test

* fix recurrent bug
test=develop

* support dlpack to tensor and implement python interface test=develop

* add unittest for _to_dlpack and from_dlpack test=develop

test=develop

* add expand_as op, test=develop

* add expand_as op,test=develop

* add expand_as op,test=develop

* add nn.py, test=develop

* delele paddle_enforce, test=develop

* refine py_reader exit, test=develop

* fix multiprocess_reader exception unittest, test=develop

* increase code coverage for legacy fluid.layers.py_reader, test=develop

* Fix docs of gru_unit and dynamic_gru.

Fix basic_gru in rnn_impl.py.

Add error messages for param_attr setting in layer_norm api.

Add int64 dtype for expand.

test=develop

* Reopen unit-tests of basic_gru/basic_lstm in rnn_impl.py.
test=develop

* Add unit test for layer_norm api.
test=develop

* Remove the deprecated gru doc fix. test=develop

* Fix basic_gru test coverage. test=develop

* Update API.spec. test=develop

* Update API.spec. test=develop

* Fix test_basic_gru coverage test. test=develop

* Update test_basic_gru in test_layers to use fluid.data
test=develop

* Update test_basic_gru for coverage. test=develop

* Refine error message of transpose.
* Fix transpose, multiplex, unsqueeze, unstack. test=develop, test=document_preview, test=document_fix

* fix the error message of zeros op
test=develop

* Fix unittest of zeros op
test=develop

2. fix bug in backward.py: using fill_constant instead of fill_constant_batch_size_like
3. fix bug in ExpandGradOp.

test=develop