* temporally disable zero_copy

* add test

* follow comments

* fix calcu_gradients

* fix code place

* fix embedding interface usage

* support to_static(model)

* add warning and unittest

* Use the single GPU card to execute the test_fuse_bn_act_pass UT.

* add double grad for tile, test=develop

* add double grad for expand_v2 op, test=develop

* add double grad for expand, test=develop

[UT] fix run type of ut test cases of test_train_recognize_digits and test_api_impl, test=develop (#27218)

* - introducing oneDNN 1.6

test=develop

* - Removed redundant code

test=develop

* add some unittest cases ot verify jit.save, no_test

* add more unittests

* add test with example inputs

* polish implement details

* remove useless blank

* fix fetch random error

* parameter_server_optimizer support auto_strategy

 fix the CudaPinMemory bug for the equal op and add the test case for the equal op

Decrease the number of running iterations to reduce CI time.

CI system shows it decreased the unittest time from about 90 seconds to about 30 seconds

update error info for selected_rows_functor

add lars to fleet meta optimizer

* refine launch and distributed repr string for print

* set default value to strategy in distributed_optimizer test=develop

* update requirements.txt

* add unittest_py directory and add new requirements.txt file,test=document_fix

* add unittest_py directory and add new requirements.txt file,test=document_fix

* Add naming rule if not specific InputSpec.name

* fix function name typo

* refine comment

* remove print statement

optimize the error message for math dir