> In order to get a feasible integer solution fast I use depth first > search. > Since I have constraints of the type Sum_i (x_i) = 1, x_i >= 0, I would > like to branch up in the search. Does GLPK always branch down in the > depth first search? (In that case I can replace variable x_i by 1 - x_i > in order to simulate a branch up in the depth first search.) >
It depends on which (down- or up-) branch seems to be stronger, that, in turn, depends on the branching heuristic used. For example, if the branching on most fractional variable (--mostf) and depth first search (--dfs) are used, the branch to be solved next is that one, where integer infeasibility of the branching variable is less than in other one. You may change the default behavior either by providing your own heuristic in the callback function or by changing appropriate glpk routine (see file src/glpios09.c). _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
