Merge pull request !705 from chujinjin/add_pynative_cache

Merge pull request !775 from Etone.Chan/master

Merge pull request !494 from zhoufeng/cmake-sub

Merge pull request !501 from chujinjin/abstract_input_tensor

Merge pull request !492 from YuJianfeng/allgather

Merge pull request !390 from gukecai/master

Merge pull request !340 from ougongchang/master

Merge pull request !337 from kisnwang/optimize-execute-order-sort

Merge pull request !431 from wangqiuliang/fix-cell-ouput-issue-in-pynative

clean clang format errors and cpplint errors

add some test cases for histogram summary operator

Merge pull request !350 from lianliguang/chang-tuple-output-to-make-tuple

Merge pull request !276 from JoyLvliang/pynative-add-op-supported

Merge pull request !346 from laiyongqiang/develop

Merge pull request !274 from ZPaC/gpu-backend-supports-multiple-streams

2.GPU commnication stream and compute stream overlap.

Merge pull request !291 from caifubi/dev-getnext-mem-reuse-off

Merge pull request !260 from lianliguang/refactor-padding-strategy

Merge pull request !203 from kisnwang/optimize-allreduce-mem-malloc

Merge pull request !109 from leonwanghui/typo-fix

Signed-off-by: leonwanghui <leon.wanghui@huawei.com>