Re: [Help-glpk] Regarding selecting a next node for branching

[Andrew Makhorin]

> I use " glp_ios_branch_upon(glp_tree *tree, int j, int sel) " to
> select a next variable to branch on. 
> Here I set int sel = GLP_NO_BRNCH which says that it uses general
> selection technique.
> 
> Can you please tell when it uses general selection technique, does it
> use a heuristic suggested by Tomlin
> to select next branch based on pseudo-costs or anything else?

If you call glp_ios_branch_upon, the mip solver branches on the variable
chosen by you, so in this case the branching heuristic specified by the
br_tech control parameter is *not* used.

> 
> Also, if for any other method of variable selection which I implement,
> how can I use same technique to select next branch?
> Do I need to copy the subroutine branch_drtom to my code and then say
> int sel = GLP_NO_BRNCH wherever it says
> select up or down branch to branch on?
> 

In principle, yes. Note, however, that Driebeck-Tomlin's heuristic
includes not only choosing a branching variable, but also choosing the
branch to be solved next.