* add cpu version, using set: sum, min, max

* add cpu version: mean

* improve cpu code and fix dynamic memory allcation problem

* fix arg error, add index judge, delete fp16

* fix bug in CudaAtomicMax and CudaAtomicMin

* add CUDA version

* fix grad_op bug for index

* add op test, add correct cpu grad op

* Add correct CUDA Mean grad

* [Add] Successful MEAN and SUM

* [Add] Successful MIN and MAX in CPU

* [Add] Successful MIN and MAX in CUDA

* fix windows dtype ci

* fix ROCM ci by adding HIP flag

* rename fused_gather_scatter to send_recv

* unify name as send and recv

* change zero index return time

* add send_recv incubate api

* fix index data type, add unittest case for API

* delete redundant input tensor

* fix en example and docs, add default value in pool_type

* add shape judge and max grid judge

* fix comment

* fix index type bug

* add const &

* fix en docs

* delete numpy in examples

* add unittest for int input

* fix send_recv comment

* change send_recv to graph_send_recv

* replace and remove complex64/128 types in custom OP and other files

* fix custom_tensor_test fail bug

* fix custom_conj_test fail bug

* fix dispatch_test_op build fail bug

* add support for complex grad accumulated

* add unittest for coverage

* update test dtype

* remove useless blank line

fix cpplint error for the autmic max/min

fix cuda atomic for ARCH<350 for the automic_max

Add GPU Kernels of Segment Ops,  support, sum, max, min, mean

* "rewrite the test case"

* "follow comment"

* cherry picked

* "cherry picked platform"

* "add comment"

* "fix ci"

* fix __shfl_down_sync_ of cross_entropy

* use reduceSum

* "fix ci"

* "re-commit "

* "picked up"

* "fix ci"

* "fix pdb hang up issue in cuda 9"

* add cuda_device_functions.h

* move reduceSum to elementwise_op_function.h

* Support int64 for sum op

* Refine code

* refind accuracy_op

* follow comments

* follow comments

1. finish lookup table CPU and GPU kernel
2. Add some cuda helper
3. Add some math funtor