I don't really need to maximize the flow.

I only need to find a feasible one. So do this.
Extend FindFeasibleFlow to return feasible flow shortage.
Use maxflow RI generator by default.
Introduce SearchParam structure.
Get rid of R local search code temporarily.

I will still need a simpler version of it a little bit later.
A function to release "max vbuckets per tag" constraint.
Allow relaxing "max vbuckets per tag" constraint.
Name variables of type R and RI uniformly everywhere in the code.