* add support to gcc8, add docker env test=develop

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

* Revert "Refactor conv computeINT8 (#19574)"

This reverts commit 2c32c2d6.

test=develop

* replace PADDLE_ENFORCE
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modify the way to pass parameter out_size in function. 

* - Flushing mkl-dnn cache

test=develop

- Disabled clearing cache for LoadModel

- Added clearing of mkl-dnn cache when Executor is created

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- Do not clear for GPU places

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- compilation fix

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* - Moved clearing of mkl-dnn cache in destructor of executor

test=develop

* - Compilation fix

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- Reverted conditional clearing of mkl-dnn cache in Executors's
  destructor

test=develop

- compilation fix

test=develop test=document_fix

* improve save and load behaviour, test=develop

* code cleaning, test=develop

* disable check_guards and update_guards in release version, test=develop

* fix compilation issue, test=develop

* add buddy_allocator speed test data, test=develop

* fix compilation issue, test=develop

* fix comment, test=develop

* update function names according to the google C++ style guide, test=develop

* tweak the test data format, test=develop

* move buddy_allocator_test_data to paddle/fluid/testdata, test=develop

* add accessor and mutator for Desc, test=develop

* refine reduce code to save compiling time and binary sizes, test=develop

* add reduce rank check to avoid bug, test=develop

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

test=develop

* 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

* add condition judgement for performance improvement test=develop

* add condition judgement for performance improvement test=develop

* refine code style test=develop

Add IndicateVarDataType interface to block tensor is not initialized problem in OP GetExceptedKernelType (#20044)

* add indicate_var_data_type inferface, test=develop

* add unittests & polish error message, test=develop

* remove needless include, test=develop

* extract public function & polish message, test=develop

* delete empty var check, test=develop

* change data_type to pointer parameter, test=develop

* polish details, test=develop

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

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* 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

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>