Add tests to use dy/dx to make sure the gradient values calculated by the control flow backward is correct. Also fixed bugs detected by those tests.

Fix bugs:

1. Unlike sum_op, optimizer ops don't allow uninitialized input tensor. But in conditional_block_grad_op, since the conditional_block may not run, the output gradient tensor may be uninitialized, which will cause the optimizer op error. To fix it, we should let optimizer ops support uninitialized input like sum_op or assign the uninitialized gradient to 0 when the conditional_block_grad_op doesn't run. I found there are about 10+ optimizer ops. **To be simpler, I just assign output gradient of the conditional_block_grad_op to 0 in this PR**. But it can be further explored whether we can make optimizer ops like sum_op to support uninitialized input tensor because theoretically we can speed up without the assigning in conditional_block_grad_op.

2. Infer parameter shapes during append_backward. I didn't know that all our parameters are in global block. When op_desc is inferring shapes at the sub-block, it may not know the shape of gradients of parameters whose shape information is at global block. I fixed it by inferring shapes of gradients from forward var.

This PR also did some code clean up:
1. Print the var name when sgd_op catches shape error so that it is easier to debug
2. Fix a typo: dicta -> dict

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* - BAtch norm mkl-dnn NHWC

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- compilation fix

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- UT fix

- cosmetics

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- Fix to Batch Norm MKL-DNN NHWC UT

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Conflicts:
	paddle/fluid/operators/batch_norm_op.h

* - Lint fixes

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* dygraph Embedding layer use lookuptable v2
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* fix test_nce
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* fix fill_constant_batch_size_like_op precious problem  test=develop

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* set dim[0] to -1 if dim[0] < 0 and remove assertion to runtime, test=develop

* modify ENFORCE message, test=develop

* add validation for x.shape[0] > 0, test=develop

* add ut, test=develop

* fix -Wno-error=sign-compare warning in gcc8

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* fix warning in distributed codes

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* fix transpose conv,test=develop

* fix comments
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* refactor AUC OP and add its CUDA Kernel
* the layout of global auc doesn't change

* fix the device supported of the op unique and unique_with_counts.
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test=document_fix

* Fix the precision of test in the op of unique and unique_with_counts.
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test=document_fix

* fix shape check in density_prior_box, test=develop

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* add unused input vars check for OpWithKernel, test=develop

* remove unused vars in some ops, test=develop

* fix batch_norm, test=develop

* add white list, test=develop

* add CI check for white list, test=develop

* :ove white list to c++, test=develop

* solve failure of CI, test=develop

* add unittest for unused_var_check, test=develop

* refine code, enable check in operator_test, test=develop

* skip mkldnn, test=develop

* extend white list, test=develop

* refine condition of mkldnn, test=develop

* fix paddle_build, test=develop

* follow comments, test=develop

* fix GetExpectedKernelType

* add wiki ref to err_msg, test=develop

* follow comment, test=develop

* add param & grad shape check for sgd op

* add _reshape_inplece interface for dygraph parallel

* refine unittest based paddle/models scripts, test=develop

* add unittest for parallel grad fuse, test=develop

* Commit before merging develop

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* Backup after working with Huihuang logs

* Commit before deleting Huihuang debug loggings

* Commit before debug

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* Fix bug commit

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* Backup of fixing bugs

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* Clean up code

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* Fix a bug in sum_op

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* Add ascending for argsort

* Refine api doc description.

* Refine descending description

* Add int32 logic to speedup when data is small size.

* Remove int32 opt as not support in python

* add_dygraph_execution_context

* add dygraph infershape context and execution context; test=develop

* fix imperative bug; test=develop

* remove inputs outputs interface from execution context,
because it have same function with inputNames;
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* remove tracer_test ctest; test=develop

* fix split op bug; test=develop

* fix unitests bug; test=develop

* fix distribute test bug; test=develop

* fix ngraph compile bug; test=develop

* fix grad maker bug; test=develop

* fix load op bugs; test=develop

* fix operator.cc construct bug; test=develop

* remove useless name find in operator; test=develop

* add tracer_test; test=develop

* fix concat, split bug; test=develop

* remove tracer_test unitest; test=develop

* fix attribute check bug; test=develop

* add test code to fix converage; test=develop

* remove useless code, change check backward input in engin; test=develop

* unlock var type infer shape;test=develop

* add ShareAllLoD api; test=develop

* add dygraph infershape context unitest; test=develop

* remove increase and decrease lod in dygraph; test=develop

* addd override; test=develop

* fix increase descrease lod; test=develop

* fix paddle_enforce; test=develop

* disable lod op dygraph check; test=develop

* fix paddle enforce error; test=develop

* add comment for op_registry and OperatorBase; test=develop

* optimize the comment of op_registry; test=develop

* fix format of comment; test=develop

* fix format of comment; test=develop

* optimize the format of comment; test=develop

* optimize the format of the comment; test=develop

* optimize comment of op_registry; test=develop

remove nccl related code in windows

* add Adam beta1/beta2 support Variable. test=develop

* use system allocator in unittests, test=develop

* fix op bugs, test=develop

* fix tensor copy bug when src and dst are the same, test=develop

* batch_norm momentum support variable. test=develop

* fix format. test=develop

* add batch_norm momentum variable example. test=develop

* move MomentumTensor to training branch. test=develop

* split example. test=develop

* fix doc. test=develop

* fix PADDLE_ENFORCE ci. test=develop

* fix format. test=develop

* add lod information, test=develop

* add lod, test=develop

* fix lod, test=develop

* fix lod, test=develop

* remove -Wno-error=sign-compare, make warning as error

test=develop test=document_fix

* fix exist compile warning

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* fix ref_cnt pass, test=develop

* add cpp unittests to reference_count_pass, test=develop

* follow comments, test=develop

* support data_norm_op run in CUDA
* add two parameters sync_stats & summary_decay_rate
* add UT

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* Implement Int8 FC

* Integrate FC into INT8v2

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* int8 FC: transpose weights before computing scales

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* Add support for activation_type string in FC

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* Disable MKL-DNN's FC in VGG16 and 19

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* Disable FC quantization when mkldnn FC is disabled

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* Solve PADDLE_ENFORCES in FC int8

* Fix Paddle enforces and remove const cast

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* Fix style changes

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* Fix quantizer_tester test and add fc quantization

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* Fix FC test fail on CUDA

* Remove unnecessary log from quantize placement pass

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* Add Thread ID to FC hash key

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* Add comments to MKL-DNN FC Kernel

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* Refactor quantizer

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* Fix linter issues

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* Fix crash in slim googlenet

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* Fix PADDLE_ENFORCE messages

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