private async Task <InferenceResults <Tval> > ReduceDomains(ConstraintSatisfactionProblem <Tval> csp, Queue <Tuple <Variable <Tval>, Variable <Tval> > > queueOfArcs, InferenceResults <Tval> inference = null, bool stopAtInconsistency = true)
{
inference = inference ?? new InferenceResults <Tval>();
while (queueOfArcs.Count > 0)
{
Tuple <Variable <Tval>, Variable <Tval> > arc = queueOfArcs.Dequeue();
Variable <Tval> X = arc.Item1, Y = arc.Item2;
if (await Revise(csp, X, Y, inference))
{
if (X.GetDomain().Size() == 0)
{
inference.InconsistencyFound(X);
if (stopAtInconsistency)
{
return(inference);
}
}
foreach (Variable <Tval> neighbour in csp.GetNeighboursOf(X))
{
queueOfArcs.Enqueue(new Tuple <Variable <Tval>, Variable <Tval> >(neighbour, X));
}
}
}
return(inference);
}
public override async Task <InferenceResults <Tval> > RemoveVariable(ConstraintSatisfactionProblem <Tval> csp, Assignment <Tval> assignment, Variable <Tval> variable, Domain <Tval> default_domain = null)
{
if (csp == null)
{
throw new ArgumentNullException("csp");
}
if (assignment == null)
{
throw new ArgumentNullException("assignment");
}
if (variable == null)
{
throw new ArgumentNullException("variable");
}
if (assignment.HasBeenAssigned(variable))
{
Tval oldValue = assignment.ValueOf(variable);
assignment.RemoveAssignment(variable);
List <Variable <Tval> > neighbours = csp.GetNeighboursOf(variable);
foreach (Variable <Tval> v in neighbours)
{
// to preserve consistency of the domains it is neccessary
// to add back the old value only when it's fitting
if (!assignment.HasBeenAssigned(v) || assignment.ValueOf(v).Equals(oldValue))
{
v.GetDomain().GetValues().Add(oldValue);
}
}
variable.UpdateDomain(default_domain ?? new Domain <Tval>());
}
return(await inferenceStrategy.Infer(csp, false));
// there are difficult edge cases that an inference limited
// on the neighbours can't solve
// return inferenceStrategy.Infer(csp, variable, default(Tval), null, false);
}