* cache core.ops, test=develop

* refine, test=develop

* add scatter-gather opt

* fix topo for pp

* rename function

* kill process by group

* pipeline adaptive for heterps;test=develop
* fix finalize hang;test=develop
* add is_compiled_with_heterps for dataset;test=develop
* fix hashtable core when pass ins_num=0;test=develop

* add amp support for pp

* add amp untest

* fix hdfs and fleet_util for supporting save/load infer;test=develop

* add random and prevent deadlock

* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* elastic unitest

* rename demo

* del py2 code2

* fix test timeout

* elastic etcd ready

* add pplayer

* add sharedlayerdesc

* update, test=develop

* add parallel_cross_entropy

* add grad for crossentropy

* fix cross entropy

* modify API nn.Bilinear's doc, test=develop

* fix c_split bug

* fix utest

* add c_embedding for tensorparallel

* Dygraph Recompute support AMP

* dygraph recompute: update unitest

* support ssd in PsCore

* remove log

* remove bz2

* defalut value

* code style

* parse table class

* code style

* add define