* Add a StatValue class in the backend to represent a stat.
* Add a singleton StatRegistry to maintain the collection of stats.
* For the sake of code neatness, we only support type of int and float, which can cover most of the scenarios.

* refine err_msg of pybind.cc, test=develop

* refine err_msg in tensor_py.h, test=develop

* refine error msg, test=develop

* fix test_exception, test=develop

* follow comments, test=develop

* support selectedrows allreduce in multi-cards dygraph, test=develop

* remove useless import modules in unittests, test=develop

* add nccl cmake to get nccl version, test=develop

* add if-condition to compiled correctly, test=develop

* add detail version parseing for old nccl, test=develop

* polish camke details, test=develop

* fix remove test cmake error, test=develop

* fix cmake condition, test=develop

* change unittest camke list, test=develop

* fix unittest cmake rule, test=develop, test=framep0

* add amp_check_finite_and_scale op, test=develop

* add cpu kernel, test=develop

* use bool, test=develop

* follow comments, test=develop

* remove REPLACE_ENFORCE_GLOG compile option & add ci rule prohibit LOG(FATAL) using, test=develop

* remove ci test case, test=develop

* replace all LOG(FATAL) & polish message, test=develop

* fix typo, test=develop

* polish error info detail, test=develop

* add crypto helper for paddle, test=develop

* cryptopp.cmake bug fixed, test=develop

* remove debug build type, test=develop

* fixed CMakeLists for new target, test=develop

* fix CI bug, test=develop

* add cmake option flag DWITH_CRYPTO, test=develop

* add crypto api for python, test=develop

* Revert "add crypto api for python, test=develop"

This reverts commit 3a1cfa9d.

* Revert "Add crypto api (#24694)"

This reverts commit 5a7a517c.

* Revert "Revert "Add crypto api (#24694)""

This reverts commit f952b19f.

* fixed cryptopp cmake building error, test=develop

* change WITH_CRYPTO building option to OFF, test=develop

* â€fixed cipher test failed, test=develop

* "add crypto api for python, test=develop"

This reverts commit 83fb55c0.

* travis CI bug fixed, test=develop

* fixed test in python3

* test=develop

* fixed unittest, test=develop

* Support AucRunner in PaddleBox
* update some code style

* fix bug of varbase.__getitem__, test=develop

* fix bug of float and other type, test=develop

* Add InitializeGPUAndLoadModel to solve random hang when downloading sparse parameters.
* Update SaveBase to solve test problem.

* add new macro BOOST_GET_SAFELY & unittests, test=develop

* add different macro type, test=develop

* fix get macro type in executor, test=develop

* four macro part change backup

* using one macro for all case, test=develop

* revert attribute change, test=develop

* change to three func to solve gcc4.8 bug, test=develop

* polish some details, test=develop

* raise index error when slice out of range; test=develop

* add uni test; test=develop

* fix format error; test=develop

* add comment for py::index_error; test=develop

* polish error message; test=develop

* polish error message; test=develop

* solve mklml memory leak on windows

test=develop

* remove unused msvcr120.dll

test=develop

* add timeout and http store in communication, add revert and confirm in fleet
* test=develop

* update name generator, test=develop

* use c++ unique name generator, test=develop

Fix the dygraph mode in matmul, add the support in Linear Op

* add DataLoader, Dataset, BatchSampler

* Support LoDTEnsorArray in fetch op

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* Support LoDTensorArray in fetch

test=develop

* add save with prefix
* test=develop

* fix init_gflags with 'python -c', test=develop

* enhance error msg related Tracer, test=develop

* refine err msg, test=develop

* follow comments, test=develop

* Involves AfsAPI to resolve slow downloading.
* Mainly used in PaddleBox

* Remove the NGraph engine from PDPD repository
1. Each operator was removed from the operator's directory
2. Each test was removed from the unittest directory
3. The parallel executor support was removed from the PDPD
4. The CMake file was removed from the PDPD
5. The NG flags were removed from the repository
test=develop

* Remove ngraph from:
1. Cmake file
2. Python file
test=develop

* polish api program error message, test=develop

* fix condition error, test=develop

* fix test prune error, test=develop

* fix coverage problem, test=develop

* change the cmake and apis of lite engine, test=develop

* change the cmake of lite engine, test=develop

* Add a function to update FLAGS

test=develop

* Add a function to update FLAGS

test=develop

* expr flags

* Add a function to update FLAGS

test=develop

* distinguish public/private vars, test=develop

* fix windows issues, test=develop

* expr flag

* Add functions to get and set FLAGS

test=develop

* Add functions to get and set FLAGS

test=develop

* Add functions to get and set FLAGS

test=develop

* Add functions to get and set flags

test=develop

* Add functions to get and set FLAGS

test=develop

* Add a function to update FLAGS

test=develop

* Add a function to update FLAGS

test=develop

* Add functions to get and set flags in Paddle

test=develop
Co-authored-by: Nsneaxiy <sneaxiy@126.com>

* add paddleboxdatafeed
* add ifdef linux and boxps
* add untest for datafeed
* fix untest of test_paddlebox_datafeed
* fix untest
* rename function

* 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

* prune train program by fetch_list, test=develop

* add unittest for prune, test=develop

* fix pruned feed, test=develop

* support ParallelExecutor and feed prune, test=develop

* add comments, test=develop

* update unittest, test=develop

* update unittests, test=develop

* remove debug code, test=develop

* support cond in clone, test=develop

* support cond in prune, test=develop

* support multiple minimize, test=develop

* support cache, test=develop

* fix _copy_param_info_from, test=develop

* support python2 str, test=develop

* remove debug code, test=develop

* fix bug of caching CompiledProgram, test=develop

* fix multi_device issue, test=develop

* tmp

* support tuple in fetch_list and overriding use_prune, test=develop

* dont use nonlocal in python2, test=develop

* remove nonlocal, test=develop

* code clean, test=develop

* code clean, test=develop

* feed list, test=develop

* test adam, test=develop

* follow comments, test=develop

* reduce duplicate code, test=develop

* update comments, test=develop

test=develop