Re: [Help-glpk] Number of simplex iterations

[Andrew Makhorin]

> I am implementing strong branching using GLPK.
> While determining the branching variable from the set of candidate
> variables, I calculate LP
> relaxation at each child node.
> 
> 
> I want to fix the bounds of the variable if one of the child nodes is
> infeasible.
> I tried doing this as follows:
> glp_set_col_bnds(glp_ios_get_prob(tree), j, GLP_FX, 1.0, 1.0);
> (where j is the candidate variable for which one of the child nodes is
> infeasible. I am doing this 
> in a subroutine where I determine set of candidate variables and
> select a variable to branch on. This subroutine is called
> by callback routine using GLP_IBRANCH)
> 
> 
> However, When I try to do this, I get error by glpk pointing to the
> branch_on routine in glpk source code.
> 
> 
> Can you please guide me how can I fix the bounds in strong branching.
> 

You cannot change the active problem object in that way, because it is
used by the mip solver. To implement a strong branching you need to use
a copy of the current subproblem created with glp_copy_prob.