Merge pull request !2954 from Kang/optimization

This reverts commit 02dd305b.

Merge pull request !2951 from guozhijian/update_r0.3.1_release_notes

Merge pull request !2944 from wandongdong/master

Merge pull request !2779 from chenweifeng/ctcloss

Merge pull request !2765 from fary86/fix_large_for_loop

Merge pull request !2915 from Xiaoda/8-move-embeddinglookup-external

Merge pull request !2946 from EricZ/emtpy-tensor

Merge pull request !2926 from islam_amin/object_ops_cc_ut_floats

Merge pull request !2833 from nhussain/engine_validators

new test case

Name change for empty check

fixed random_apply tests

fix validators

fixed random_apply tests

fix engine validation

Merge pull request !2892 from tony_liu2/master

Merge pull request !2922 from ava/float_change

Merge pull request !2940 from zhangdengcheng/master

Merge pull request !2929 from jiangjinsheng/issue_fix4

Merge pull request !2917 from chenzhongming/master

Merge pull request !2895 from fanglei/case

Merge pull request !2605 from XunDeng/pp_poc_v3

Merge pull request !2887 from JoyLvliang/back-to-fusedbatchnorm-operation-in-pynative-mode

Merge pull request !2921 from kisnwang/optimize-two-level-reduce-sparse-gradient

Merge pull request !2928 from YuJianfeng/master

Merge pull request !2869 from jinyaohui/master

Merge pull request !2913 from jiangjinsheng/issue_fix4

Merge pull request !2904 from qianlong21st/change_icu_compile

Merge pull request !2909 from Kang/master

Merge pull request !2816 from Kang/optimization