[Cbc] CBC

[Nathan Petty]

As a follow on question, if the answer to the original question is that
there is indeed a starting condition that will result in the solution path
being the same in multiple runs, is there also then a starting condition
seed that will guarantee a different path?  This would also be very helpful
because I could start multiple solvers with different seeds in order to
generate a family of optimal paths.

On Thu, Sep 7, 2017 at 1:39 PM, Nathan Petty <nathanlpetty at gmail.com> wrote:

> 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
>
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