add op_kernel_type_test

rm unsed RegisterOp method in OpRegistry

fix math_function warning

fix doc

"remove hash combine"

* refine OpKernelKey

* refine codes

* fix code style

* follow comments

* "change operator interface"

* "move devicepool to device_context"

* "fix operator test"

* "fix op_registry Run interface"

* "net op passed. Need to fix nccl multi-Context"

* "add nccl group function"

* "add nccl group function"

* "fix gpu count exceed 32 error"

* "fix recurrent op, nccl op"

* "change the other operators interface with Place"

* "fix typo"

* "fix pybind"

* "fix device in python side"

* "fix pybind failed"

* "add init for test"

* "fix CI"

fix doc.

Update annotations of layers.py.

fix doc.

fix doc.

Refine fluid recommender test

remove unused usage_stat script

add python wrapper for sequence_pool

Add ReorderLoDTensorByRank

* add data layout

* fix ci

Add python wrapper for reduce_mean

fix cmake require docs

[Done] API for dist train

fix the latex equation in fluid fc layer.