// //////////////////////////////////////////////////////////////
// inference algorithms
/// <summary>
/// Implements forward checking.
/// </summary>
/// <param name="var"></param>
/// <param name="assignment"></param>
/// <param name="csp"></param>
/// <returns></returns>
private DomainRestoreInfo DoForwardChecking(Variable var,
Assignment assignment, CSProblem csp)
{
DomainRestoreInfo result = new DomainRestoreInfo();
foreach (IConstraint constraint in csp.GetConstraints(var))
{
IList <Variable> scope = constraint.GetScope();
if (scope.Count == 2)
{
foreach (Variable neighbor in constraint.GetScope())
{
if (!assignment.HasAssignmentFor(neighbor))
{
if (this.Revise(neighbor, constraint, assignment, csp,
result))
{
if (csp.GetDomain(neighbor).IsEmpty())
{
result.SetEmptyDomainFound(true);
return(result);
}
}
}
}
}
}
return(result);
}
public DomainRestoreInfo ReduceDomains(Variable var, object value, CSProblem csp)
{
DomainRestoreInfo result = new DomainRestoreInfo();
Domain domain = csp.GetDomain(var);
if (domain.Contains(value))
{
if (domain.Count() > 1)
{
FIFOQueue <Variable> queue = new FIFOQueue <Variable>();
queue.Push(var);
result.StoreDomainFor(var, domain);
csp.SetDomain(var, new Domain(new object[] { value }));
this.ReduceDomains(queue, csp, result);
}
}
else
{
result.SetEmptyDomainFound(true);
}
return(result.Compactify());
}
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);
}
}
}
}
}
