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This adds a `TODO` comment according to https://github.com/PaddlePaddle/Paddle/issues/13550#issuecomment-430133585

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This can cause a lot of problem:
1. Wrong operator implementation, Op can get a wrong type without failure.
2. Anytype can be Get without defined in VarType.

Also fix wrong STEP_SCOPE usage.

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* set the right shape of selected_rows
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* enhance check

* fix activation_op

* remove cast

* use ShareDimInfo replace SetDim and ShareLod

* use ShareDimAndLod
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* follow comment

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* check whether the input has lod
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* Split ShareDimAndLod

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* checkout clip.py
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* "avoid copy back to cpu"

* "add infinity support"

* "fix ci"

* "add cpu macro"

* rerun ci; test=develop

* "fix api"
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review fix

review from hshen14 fix

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fix error in broadcast and code cleanup

rename bias -> eltwise and added macro to shorten code

formatting

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* "fix operators cmake"

* "rerun ci"
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This reverts commit 21bb9e91, reversing
changes made to 3fa68dc1.

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scope's API modifies its internal state. And scope's
API can be called from multiple threads during traing.
Hence, we need locks to protect the scope's internal
states.

We can optimize it in the future. But the current
solution is buggy.

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- add naive executor
- fix concurrency performance issue