- First implementation of BWD and FWD of pooling mkl-dnn

- Compilation fix

- Fix

- Fix

 - Fix

- Fix to crash

- Compilation fix

- Combined AcquireBacward with Fwd

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* give warnings when save a model without any parameters test=develop

* delete one line comment test=develop

* add py_reader combination unittest,test=develop

* follow huihuang's comments, test=develop

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* make OpTest check grad inplace even if forward has no inplace, test=develop

* do not run PE when enable_inplace is False, test=develop

* add conv3d cuda kernel for float16 type, test=develop

* refactor OpTest for inplace, test=develop

* add comments, test=develop

* add fake_quant_dequant_op for average pool2d
* add test

* add recompute based checkpoints methods for large batch training
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* add append_backward_with_forward_recomputation
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* refine optimizer
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* update backward and optimizer
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* make Variable usable
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* add recompute code

* refine optimizer
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* refine addup _append_backward_ops_with_checkpoints_
1) for recompute part, just cache the grad_op_desc without appending to block
2) before appending grad_op_desc to backward part, addup_repetitive_vars, remove unused branch
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* make method private

* add recompute strategy into DistributedStrategy
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* checkpoint version3
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* remove some print information
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* remove unused sumop
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* try to fix recompute with graph building modules

* add input names to vars should be held

* add memory debug tool

* backup backward

* Fix bugs

* add backward desc for op not in any segments

* add exception info for sub_block

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* modify code style

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* modify code style

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* remove print functions

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* add API spec

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* make Recompute a child class of Optimizer

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* add API spec

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* modify API spec

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* add document for Recompute

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* change API doc of Rcompute

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* code cleaning

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* modify API spec

* fix bugs when segments hold no element

* add testcase for Recompute Optimizer

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* add test for apply_gradient, and code cleaning

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* add test case for load function

* enable CI

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* add test case

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* add sample code for 4 function of recompute optimizer

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* Add RecordHistoryLocalExecScopes
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* remove the useless warning for user to avoid confuse test=develop

* optimize the error information when the input for while op has a wrong shape test=develop

* add mse_loss op

* add op compatible infomation; test=develop

* add enum type

* add enum type; test=develop

* fix softmax ce time limit check failed. test=develop

* refine softmax calc. test=develop

* move tree_conv to fluid.contrib.layers

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* update API.spec for tree_conv

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* update tree_conv api to increase unit coverage

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* unify DataLoader APIs, test=develop

* integrate iterable CPU Dataset, test=develop
add GPU dataset supporting, test=develop

* add unittests for dataset, test=develop

* add more docs to dataloader apis, test=develop, test=document_preview

* refine doc, test=develop

* refine doc again, test=develop

* increase coverage, test=develop

* optimize cloud rolemaker, test=develop

* add instance norm op

* refine reallocate of workspace size, test=develop

* add lock to cudnn handle calls, test=develop

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* Initial, functional commit

* Clean commit related files
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* refactor dygraph,test=develop

* fix failed unittest,test=develop

* polish code,test=develop

* check windows ci error,test=develop
try to fix windows ci error by np.allclose,test=develop

* polish vlog and profiler, test=develop

* try to fix preceding ops order,test=develop

* test transformer in windows ci, test=develop

* use python c-api to speed up tracer.trace,test=develop

* test=develop, fix docker with paddle nccl problem

* test=develop, add ut for debug string and gradient_accumulator

* test=develop, add tests for layer/gradient_accumulator/prepared_op

* test=develop, fix complie error for test_prepared_op

* test=develop, add more ut for dygraph

* test=develop, create API.spec for dygraph api change

* test=develop, refoctor name to make it easier to understand

* test=develop, refoctor name to make it easier to understand

* test=develop, fix multi-gpu failed problem , add Tracer tests, change PADDLEENFORCE to PADDLEENFORCE_EQ

* test=develop, fix ut failed on parallel se-resnext

* test=develop, change one more PADDLE_ENFORCE

* support auto prune in dygraph mode

* test=develop, support auto prune

* test=develop, merge develop conflict

* test=develop, fix test_layer and test_tracer ut

* test=develop, fix bug which may cause stop_gradient disabled with a list of backward inputs

* add TRT shape check, test=develop

* model_input_shape == runtime_input_shape, refine message, test=develop

* fix trt bugs when sharing params, test=develop

* add unittest for cascade_rcnn

* refine err msg of out of gpu memory, test=develop

* refine err msg again, test=develop

* refine errog message again, test=develop

* follow reviewer's comments, test=develop

* support 2-level lod of input in sequence_pool test=develop

* fix lod level bug in .cu test=develop

test=developt

1. group_norm support data_layout=NHWC
2. modified doc of group_norm

* Set states of recurrent op as dependent vars in prune of save inference model

This PR will fix the save/load inference model problem of RNN models.

The reason of the bug is that save_inferenc_model will prune OPs that doesn't contribute to Output. But in recurrent_op, States are not Output, OPs refers States will be pruned. 

This fix adds States of recurrent_op as dependent var so that OPs referring States won't be pruned.