* branch init

* logical graph

* chain graph with bp struct

* backward done

* loss record struct

* build model struct

* compute task node

* fix bugf

* GenSortedCompTaskNodes

* clone op with boxing thread

* BuildSubTaskGraphMethod

* remove addclone for data_loader

* copy task node

* task graph build done

* fix boxing

* add TODO

* update

* update

* MaxModelSplitNum

* data part num

* DataConcatAndDataSplit


Former-commit-id: 8ed98d5c