Re: [Help-glpk] generalized branching with IOS

[Andrew Makhorin]

> I was looking at the IOS API and the column generation part is
> simple. The 
> problem is that it is very inconvenient to branch in one of the
> variables. It 
> would mean to fix a independent set an being present or not in
> the final 
> solution. The branches are very unbalanced and, in the case a
> column is fixed 
> in 0, it is hard to make sure that another identical column will
> not be 
> generated.
> 
> Has someone already used a generalized branch with IOS? What do
> you think 
> about a 
> void ios_generazed_branch(IOS *ios, int ne, double *v, double
> rhs, int next);
> 
> that would add the row ( v <= rhs) to one branch and the row (v
>>= rhs + 1) to 
> the other?

You can branch on a constraint, not only on a varieble. In order to
do that you should add the constraint to a subproblem (ios allows
doing that on any level) and sets up appropriate bounds for every
child subproblems.