* static model runner basic implement, test=develop
* add run program op to execute loaded program, test=develop
* refactor static model runner & run program op, test=develop
* reset engine.cc to resolve conflict
* adapt the change of dygraph double grad, test=develop
* refactor impl to solve control flow error, test=develop
* clear debug code, test=develop
* fix ci str compatible error & checkout dygraph grad maker & add example, test=develop
* hide api & add op test, test=develop
* fix run program op test places error, test=develop
* fix program by review comment, test=develop
* delete change var desc name, test=develop
* fix other program by review comment, test=develop
* remove _static_graph_guard, test=develop
* add selectedrows test, test=develop
* remove desc parser, test=develop
* fix detail program, test=develop
* change socpe create & add test, test=develop
* test=develop, fix docker with paddle nccl problem
* don't expose numerous Tensor.set(), test=develop
* fix condition, test=develop
* fix float16 bug, test=develop
* feed should be Tensor or np.array, not Variable or number, test=develop
* use forcecast to copy numpy slice to new array, test=develop
* remove float16-uint16 hacking, test=develop
* add variable method to varbase and refactor to_variable to support return varbase
* support kwargs in varbase constructor
* add VarBase constructor to support default python args
* refine varbase initial method
* reset branch
* fix ut for change VarBase error info to PaddleEnforce
* cherry is parameter change before
* overload isinstance to replace too many change of is_variable
* rm useless files
* rm useless code merged by git
* test=develop, fix some ut failed error
* test=develop, fix test_graph_wrapper
* add some tests, test=develop
* refine __getitem__, test=develop
* add tests, test=develop
* fix err_msg, test=develop
* open dygraph op test, test=develop
* modify to_variable, test=develop
* modify input and output for dygraph, test=develop
* modify input and output for dygraph(fix bug), test=develop
* fix input processing of dygraph op test, test=develop
* fix bug, test=develop
* fix op test, test=develop
* fix forward bug for dygraph, test=develop
* fix mkldnn op test for forward, test=develop
* update nn.py for dygraph, test=develop
* fix crop_tensor_op, test=develop
* fix elementwise_mul_op, test=develop
* fix fill_op, test=develop
* fix some mkldnn op, test=develop
* open backward op test for dygraph, test=develop
* delete log, test=develop
* close backward op test for dygraph, test=develop
* fix bug for edit_distance_op and test_lstm_cudnn_op, test=develop
* fix optest backward bug for dygraph, test=develop
* fix optest backward bug for dygraph, test=develop
* close backward op test for dygraph, test=develop
* close backward op test for dygraph, test=develop
* open dygraph op test, test=develop
* fix op test for dygraph, fix GradOpDescMaker, test=develop
* fix bug for linear_chain_crf_op.h, test=develop
* remove log, test=develop
* remove log, test=develop
* remove log for op_test.py, test=develop
* remove log for op_test.py, test=develop
* fix bug for var_conv_2d_op, change PADDLE_ENFORCE, test=develop
* fix PADDLE_ENFORCE_EQ for hierarchical_sigmoid_op.cc, test=develop
* fix bug for test_increment_ngraph_op.py, test=develop
* fix lod for op test in dygraph, test=develop
* refactor op_test.py to reduce redundant code, test=develop
* fix lod optest, modify InputVar/OutputVar to HasInput/HasOutput, test=develop
* remove debug log, test=develop
* remove redundant code in base.py, test=develop
* fix some error in optest, test=develop
* fix ClearNoNeedBufferInputs function's bug for LoDTensor, test=develop
* refactor op_test.py, test=develop
* remove redundant writing, test=develop
* fix error(get tensor of the grad variable), test=develop
* fix test_concat_mkldnn test_conv2d_mkldnn, test=develop
* fix optest.py for get tensor of LoDTensor, test=develop
* fix optest.py for get tensor of LoDTensor, test=develop
* fix optest.py for get tensor of LoDTensor, test=develop
* fix some redundant code, test=develop
* reslove conflict and rewrite paddle error message, test=develop
* Add c++ global current tracer for dygraph, test=develop
* add tracer property in c++, test=develop
* support different place, test=develop
* add unittest for tracer, test=develop
* support no need buffer vars in dygraph, test=develop
* fix inference compilation error, test=develop
* update no_need_buffer_vars_inference, test=develop
* add unittests for no_need_buffer_vars_context, test=develop
* refine no_need_buffer_vars by return ref, test=develop
* polish some codes, test=develop
* test=develop, fix docker with paddle nccl problem
* test=develop, Add Variable api and refine dygraph related API
* test=develop, Add Variable api and refine dygraph related API
* test=develop, refine test for new api and error info
* test=develop, refine error info and test_layers
* test=develop, add API.spec
* test=devleop, fix to_string python2 and python3 compat error and refien doc
* test=devleop, add API spec
* test=devleop, update API spec
* test=devleop, update API spec
* test=develop, invoke ci
* test=develop, fix example code
* test=develop, update API spec
* test=develop, fix auto_prune_error_on_leaf
* test=develop, fix auto prune error on loss stop_gradient
* test=develop, remove useless error check
* test=develop, add more ut for sorted gradient