[Cbc] CBC

[Nathan Petty]

I am solving a TSP problem using CBC(2.9.9) and I have built a subtour
elimination procedure that adds subtour busting constraints and
resolves. It keeps adding these subtour elim constrains until the
solver finds a feasible optimal solution.

I save these subtour constraints in my database so that when I
resolve, they are loaded into the initial formulation, and I should in
theory not run into any more subtours because after all, it just found
an optimal feasible using this set of constraints.  But, to my
surprise, the solver finds more subtours (albiet many fewer than the
first time).  incase it matters, every variable has a unique
coefficient (driven my euclidean distance) in my obj function, so
there's a nice gradient there to slide on.

So there is something pseudo non-deterministic about the solution path
and my gut feeling is that it might be related to a starting
condition/initial solution?   So, is there a way to control that
starting condition?  Is it due to something else I am not thinking
about?

Thanks,
Nathan Petty