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user_compare_candidates

 

int user_compare_candidates(void *user, branch_obj *can1, branch_obj *can2,
                            int *which_is_better)

Description:

By the time this function is invoked, the children of the current search tree node corresponding to each branching candidate have been pre-solved, i.e., the objval, termcode, iterd, and feasible fields of the can1 and can2 structures are filled out. Note that if the termination code for a child is D_UNBOUNDED or D_OBJLIM, i.e., the dual problem is unbounded or the objective limit is reached, then the objective value of that child is set to MAXDOUBLE / 2. Similarly, if the termination code is one of D_ITLIM (iteration limit reached), D_INFEASIBLE (dual infeasible) or ABANDONED (because of numerical difficulties) then the objective value of that child is set to that of the parent's.

Based on this information the user must choose which candidate he considers better and whether to branch on this better one immediately without checking the remaining candidates. As such, there are four possible answers: FIRST_CANDIDATE_BETTER, SECOND_CANDIDATE_BETTER, FIRST_CANDIDATE_BETTER_AND_BRANCH_ON_IT and SECOND_CANDIDATE_BETTER_AND_BRANCH_ON_IT. An answer ending with _AND_BRANCH_ON_IT indicates that the user wants to terminate the strong branching process and select that particular candidate for branching.

There are several default options. In each of them, objective values of the pre-solved LP relaxations are compared.

Arguments:

Return values:

Wrapper invoked from:

select_branching_object() after the LP relaxations of the children have been pre-solved.