GitLab

* neighbor sampling draft

* val/test acc

* control variate draft

* control variate

* update

* fix new_history

* maintain aggregated history while updating new history

* preprocess the first layer, change push to pull

* update

* fix subg_degree

* nodeflow

* clear

* readme

* doc and unittest for self loop

* address comments

* rename

* update

* fix

* Update node_flow.py

* Update node_flow.py