Using rabit in conjunction with PS

[thvasilo]

Hello,

As it stands, dmlc-core can only launch either a rabit tracker or a PS.

For an experimental project I'm working I'd like to be able to do some communication over rabit (much easier to use) and some over PS (flexible programming model).

So I'm wondering if it's technically possible to have both running at the same time, and how much effort would it involve to change this exclusive assumption in the tracker.