* add KernelTypeToString interface

* cache memory in local scope

* fix typo

* refine trans logic

[WIP] new backward

Optimize the rowwise add function.

fix dist train trainspiler bugs

* "refine kernel registrar"

* "refine registrar with multikey"

* "fix register"

* "refine multikernel register"

* "fix CI"

* "fix CI"

* "fix registry"

* "swtich GPU to CUDA"

* "add register macro test case"

* "fix CI"

Refine drop_out_op and batch_norm

* add memory switch mechanism in operator kernel switch

Rename output of softmax and activations

Add data type checking for io.save_inference_model()

* init data_transform

* complete DataTransform

* fix build error

* add data_transform_test

* add a register test for data_transform_fn

* use function to simulate registration macro

* add register macro

* update test

* clean code

* restore unrelated code

* update data transform test

* generate unique name for REGISTER_DATA_TRANSFORM_FN

* add const

* follow comment

* update KernelTypePair hash function

Polish `Scope::LocalVarNames`

Fix sendrecv ut

Add python wrapper for reduce_max and reduce_min

Cannot get var name recursive since they could be same.

Refine sgd-op

Fix transpose doc

unify the indentation of license

 Speed data reader for IMDB dataset.

Refine the activation type getting in the LSTM operator to speed.