[gecode-users] Return value of Branching::commit

[Chris Mears]

Hello,

How should the return value of commit be constructed in a custom
Branching class?  In the QueenArmies example (copied below), a single
constraint is posted whose ModEvent value is converted into an
ExecStatus value by me_failed, and that ExecStatus is returned.

virtual ExecStatus commit(Space* home, const BranchingDesc* d, 
                          unsigned int a) {
    QueenArmies *q = static_cast<QueenArmies*>(home);
    const PosValDesc<bool,2> *pvd = static_cast<const PosValDesc<bool,2>*>(d);
    bool val = a == 0 ? pvd->val() : !pvd->val();
    return me_failed(Int::BoolView(q->w[pvd->pos()]).eq(q, val))
         ? ES_FAILED
         : ES_OK;
}

However, what if a commit posts many constraints?  Is it necessary to
observe the ModEvent returned by every posted constraint, and return
ES_FAILED if any of them returns ME_INT_FAILED?

(My overall aim is to implement some kind of dynamic symmetry breaking.
If a search node branches left with (X = v) and right with (X /= v), I'd
like to post additional constraints on the right branch -- for example,
if X and Y are symmetric, I'd also post (Y /= v). )