[Help-glpk] Re: variable fixing in mip solver?

[Andrew Makhorin]

>       I am wondering whether any variable fixing operation has been done
>at the nodes of branch and bound mip solver. Or it's just a normal branch 
>and bound framework based on the lp solver.

Currently neither reduced costs nor any heuristics are used to fix
integer variables. Only one variable, which is chosen to branch on, is
fixed in each node.

> How the branching variables 
>are chosen in this implementation?

By default the mip solver uses a heuristic by Driebeck and Tomlin. See
comments to the routine branch_drtom (file glplpx6c.c).