* Inception fusion operator.
* Support horizontal layer fusion in conv_fusion_op.
* Search conv algo strategy for variable-length input.
   search N times and cache the searched algos. For other input, choose the algo of input whose area is closest to this input.

* wip

* wip

* refactor no.1 dir structure test=develop

* fix linking test=develop

* fix includes test=develop

* fix build test=develop

* fix build test=develop

* refine batch merge pass

* refine batch merge pass test=develop

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* refine parallel_exe
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* rename shared_var_device

* code refine

* add test_weight_decay

* remove Sort
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* Add SortForReduce
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* code refine
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* follow comment
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add module cleanup
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This reverts commit 7f6d8ace.

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* code style fix, test=develop

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* Make topk op support variable k.
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* Fix tensor type.
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* wip

* wip

* wip

* wip for test

* add fp16 tests test=develop

* fix cpu build test=develop

* fix test=develop

* fix py3 tests test=develop

* fix lr_scheduler dtype test=develop

* fix test=dvelop

* test fix ci compile test=develop

* fix build and merge test=develop

* fallback momentumop change to general test=develop

* make fp16 lr schedule simple test=develop

* fix ut test=develop

* fix tests test=develop

* remove fp16 learning rate cast test=develop

Stack OP has much higher CPU cost than expected in release mode.
Caused by DebugStringEx() in base class OperatorWithKernel. Actually
this issue occur for each OP which hasn't implement it's own
GetExpectedKernelType().

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* refine tensor
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* refine tensor
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* fix device_context log
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