* wip

* add ref_by_trainer_id op

* ready to test

* fix ref inputs

* refine rpc_op_handle

* fix merge bug

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* remove unnecessary var_and_op
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* fix _init_zero_idx_
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* enable pyreader use pin memory

* add py reader pin memory test test=develop

* Add affine grid generator.

* fix ffine grid.

* Add unitest.

* Add CPU kernel and fix unitest.

* Fix CPU kernel.

* Refine code.
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* Fix python api.
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* Update python api.
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* Fix comment.
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* Rename affine_grid_generator to affine_grid and enhence unitest.
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* Fix unitest.
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* fix dim0 in _load_slice_up_vars

* fix dim0 in _load_slice_up_vars, fix innershape in delete_var_op

* Revert "fix lookuptable in reduce strategy"

This reverts commit 0e722c5e

* add unit test for dist

* add unit test for dist, test=develop

* cancel revert, test=develop

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* fix use_reader_alloc uts

* dist ut fixes test=develop

* update test=develop

* fix test for py3 test=develop

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- Added rough profiling

- Profiled maxpool itself

- First draft of max seqpool optimization (is_test added)

- Added unit tests to seqpool

- Cosmetic fixes

- Fix to UT of Seq pool

Disabled grad checking for sequence max pool when is_test is set to True

-Cosmetic fix to comment

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- Fix to GPU build

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- yet another GPU fix for sequence max pool

- Fix to comment

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- Change to API of sequence_pool

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- Yet another API spec change

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