[Cbc] adding to a system after solving

[John Perry]

Hi

Thanks to everyone who replied to my earlier messages. I have a followup question that should hopefully finish things for me.

In the context* I'm working on, I have to do the following:

(1) set up a system of linear inequalities;
(2) if not "done" (whatever "done" might mean),
    (2a) solve the system; and
    (2b) add linear inequalities to the system, perhaps after copying it;
    (2c) retrieve solutions to evaluate "done".

At first I tried the following approach:
(1) create si, an OsiSolverInterface;
(2) create a model m with si;
(3) if not "done",
    (3a) add linear inequalities to si, perhaps after copying it;
    (3b) solve by calling m's branchAndBound();
    (3c) retrieve solutions from si to evaluate "done".

This was problematic, for all kinds of reasons. By reading the examples carefully, I discovered that I had to retrieve the solutions from m, not from si. In addition, I can't add new inequalities to m's solver after it solves.

So it seems that what I have to do is this:
(1) create si, an OsiSolverInterfaace;
(2) if not "done",
    (2a) add linear inequalities to si, perhaps after copying it;
    (2b) create a model m with si;
    (2c) solve by calling m's branchAndBound();
    (2d) retrieve solutions from si to evaluate "done".

In short, a new model must be created whenever we want to add inequalities to a system.

Is this correct, or am I missing something?

Thanks in advance!
john perry

* The context is an interface between Coin and the Sage computer algebra system. This is  why the scenario depicted might look a little strange: it replicates how a Sage user might try to play around with a linear system. (Me, for example, but other people, too.)