public void Test_Dictionary_Not_Updates_After_Assignment()
{
var a = new Assignment <int, int>();
var d = a.AsReadOnlyDictionary();
var newA = a.Assign(v1, 2);
var newD = newA.AsReadOnlyDictionary();
Assert.AreEqual(2, newD[v1]);
Assert.IsFalse(d.ContainsKey(v1));
}
// It might be possible to parallelize this method
// giving to each task a different value of X
// but I'm not sure if it's worth it or if it creates problem with
// the paralelized IsConsistent check.
private async Task <bool> Revise(ConstraintSatisfactionProblem <Tval> csp, Variable <Tval> variableX, Variable <Tval> variableY, InferenceResults <Tval> inference)
{
bool revised = false;
Assignment <Tval> assignment = new Assignment <Tval>();
Domain <Tval> oldDomain = new Domain <Tval>(variableX.GetDomain());
List <Tval> domain_values = new List <Tval>(oldDomain.GetValues());
foreach (Tval valueX in domain_values)
{
assignment.Assign(variableX, valueX);
bool satisfiable = true;
foreach (Tval valueY in variableY.GetDomain().GetValues())
{
satisfiable = false;
assignment.Assign(variableY, valueY);
bool isConsistent = assignment.IsConsistent(csp.GetAllDiffConstraints());
if (isConsistent)
{
satisfiable = true;
break;
}
}
if (!satisfiable)
{
variableX.GetDomain().RemoveValue(valueX);
revised = true;
}
}
if (revised)
{
inference.StoreDomainForVariable(variableX, oldDomain);
}
return(revised);
}
private Assignment <Tval> CreateAssignment <Tval>(Variable <Tval>[,] variables)
{
Assignment <Tval> assignment = new Assignment <Tval>();
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
List <Tval> values = new List <Tval>(variables[i, j].GetDomain().GetValues());
if (values.Count == 1)
{
assignment.Assign(variables[i, j], values[0]);
}
}
}
return(assignment);
}
private async Task <Assignment <Tval> > Backtrack(ConstraintSatisfactionProblem <Tval> csp, Assignment <Tval> assignment)
{
if (assignment.IsComplete(csp.GetVariables()))
{
return(assignment);
}
Variable <Tval> variable = variableSelectionStrategy.SelectUnassignedVariable(csp, assignment);
foreach (Tval value in domainValueSelectionStragety.getOrderedDomainValues(variable, assignment, csp))
{
assignment.Assign(variable, value);
OnVariableAssigned(variable, value);
InferenceResults <Tval> inference = new InferenceResults <Tval>();
inference.StoreDomainForVariable(variable, variable.GetDomain());
variable.UpdateDomain(new Domain <Tval>(value));
// it should already be consistent if it reached this point
// since we make a pre-solving inference
//bool isConsistent = assignment.IsConsistent(csp.GetAllDiffConstraints());
//if (isConsistent)
if (true)
{
inference = await inferenceStrategy.Infer(csp, variable, value, inference);
if (inference.IsAssignmentConsistent())
{
Assignment <Tval> result = await Backtrack(csp, assignment);
if (result != null)
{
return(result);
}
}
}
assignment.RemoveAssignment(variable);
OnAssignmentRemoved(variable, value);
inference.RestoreOldDomains();
}
return(null);
}
// we assume that, if the variable has already been assigned,
// the old value of the variable has been removed
// by an inference at a previous step, and therefore it is not
// present in the domain of its neighbours, but since we might
// have another variable that has the same value in its neighbour
// (the assignment was not consistent) there is going to be another
// inference to rule out inconsistent domains.
public override async Task <InferenceResults <Tval> > UpdateVariable(ConstraintSatisfactionProblem <Tval> csp, Assignment <Tval> assignment, Variable <Tval> variable, Tval value)
{
if (csp == null)
{
throw new ArgumentNullException("csp");
}
if (assignment == null)
{
throw new ArgumentNullException("assignment");
}
if (variable == null)
{
throw new ArgumentNullException("variable");
}
InferenceResults <Tval> removeInference = await RemoveVariable(csp, assignment, variable);
assignment.Assign(variable, value);
variable.UpdateDomain(new Domain <Tval>(value));
return(await inferenceStrategy.Infer(csp, variable, value, removeInference, false));
}
public void Test_Constructor_Values()
{
var v = new Variable <int, int>(1, new List <int>());
var variables = new List <Variable <int, int> > {
v
};
var c = new Mock <IConstraint <int, int> >().Object;
var constraints = new List <IConstraint <int, int> > {
c
};
var a = new Assignment <int, int>();
a.Assign(v, 1);
var p = new Problem <int, int>(variables, constraints, a);
Assert.AreEqual(v, p.Variables.ToArray()[0]);
Assert.AreEqual(c, p.Constraints.ToArray()[0]);
Assert.AreEqual(a.GetValue(v), p.InitialAssignment.GetValue(v));
}