/// <summary>
/// Implements the degree heuristic.
/// </summary>
/// <param name="vars"></param>
/// <param name="assignment"></param>
/// <param name="csp"></param>
/// <returns></returns>
private IList <Variable> applyDegreeHeuristic(IList <Variable> vars,
Assignment assignment, CSProblem csp)
{
IList <Variable> result = new List <Variable>();
int maxDegree = int.MinValue;
foreach (Variable var in vars)
{
int degree = 0;
foreach (IConstraint constraint in csp.GetConstraints(var))
{
Variable neighbor = csp.GetNeighbor(var, constraint);
if (!assignment.HasAssignmentFor(neighbor) &&
csp.GetDomain(neighbor).Size() > 1)
{
++degree;
}
}
if (degree >= maxDegree)
{
if (degree > maxDegree)
{
result.Clear();
maxDegree = degree;
}
result.Add(var);
}
}
return(result);
}
private int CountLostValues(Variable var, object value, CSProblem csp)
{
int result = 0;
Assignment assignment = new Assignment();
assignment.SetAssignment(var, value);
foreach (IConstraint constraint in csp.GetConstraints(var))
{
Variable neighbor = csp.GetNeighbor(var, constraint);
foreach (object nValue in csp.GetDomain(neighbor))
{
assignment.SetAssignment(neighbor, nValue);
if (!constraint.IsSatisfiedWith(assignment))
{
++result;
}
}
}
return(result);
}
protected void ReduceDomains(FIFOQueue <Variable> queue, CSProblem csp,
DomainRestoreInfo info)
{
while (!(queue.Count == 0))
{
Variable var = queue.Pop();
foreach (IConstraint constraint in csp.GetConstraints(var))
{
if (constraint.GetScope().Count == 2)
{
Variable neighbor = csp.GetNeighbor(var, constraint);
if (this.Revise(neighbor, var, constraint, csp, info))
{
if (csp.GetDomain(neighbor).IsEmpty())
{
info.SetEmptyDomainFound(true);
return;
}
queue.Push(neighbor);
}
}
}
}
}
