Merge pull request !951 from guozhijian/fix_read_by_columns

support for 1 specific dimension to be None, added validator

fix various CI complains

another round of CI fixes

ci

refactor parts of the code

code refactor

ci fix

comments added, fix bugs

address review comments

address review comments

review cmts

added simple perf test script

update pad code

perf imprv

Merge pull request !969 from liyong126/fix_mindrecord_pk_sampler

Merge pull request !935 from zhangbuxue/develop_scatter_max_op_and_dock_ge

Merge pull request !957 from jiangjinsheng/space_to_batch

Merge pull request !322 from chenweifeng/rmsprop

Merge pull request !323 from chenweifeng/concat

Merge pull request !324 from chenweifeng/slice

Merge pull request !372 from chenweifeng/batchmatmul

Merge pull request !502 from chenweifeng/gelu

Merge pull request !516 from chenweifeng/tanh

Merge pull request !945 from chenweifeng/unary

Merge pull request !812 from jinyaohui/train_eval

Merge pull request !859 from Xiaoda/support-inferring-phase-parallel-strategy-searching

Merge pull request !934 from chenweifeng/broadcast

Merge pull request !959 from liuxiao/ops-for-VM

Merge pull request !637 from ghzl/learning-rate-make-group-mode

Merge pull request !898 from YuJianfeng/master

Merge pull request !840 from jinyaohui/conv2dtranspose

Merge pull request !904 from JichenZhao/groupn

Merge pull request !929 from cathwong/ckw_dataset_ut_cleanup

Comparison example

Added md5 and comparison example for py_transforms

Added md5 check for images

Merge pull request !909 from EricZ/test_random