/// <summary>
/// Maintenance Arc Consistency, this algorithm will check how many domain prunes are done when a assignemnt is executed
/// </summary>
/// <param name="assign">Assignment to be evaluated and updated</param>
/// <param name="neighbours">List of neighbours to start with (difference between AC3 and MAC3)</param>
/// <returns></returns>
public static bool MAC3(ref Assignment assign, CSP problem)
{
var position = assign.variable.pos;
var variableInLocalProblem = problem.vars.First(v => v.pos == position);
//Add the assignment to the problem
problem.AssignValue(variableInLocalProblem, assign.value, false);
List <Variable> queueToPrune = new List <Variable>();
queueToPrune.Add(variableInLocalProblem);
while (queueToPrune.Any())
{
//Get the first variable
var headVariable = queueToPrune.First();
queueToPrune.Remove(headVariable);
//Get the neighbours of the variable
List <Variable> neighbours = problem.GetNeighbours(headVariable).Where(n => !problem.IsVariableAssigned(n)).ToList();
//Loop over neighbours
foreach (var neigh in neighbours)
{
//Get the list of values to delete for conflict
List <OverFloorType> valuesToPrune = new List <OverFloorType>();
//Check if value is compatible with remaining values in head
foreach (var valPruned in MAC3HeadTailChecker(headVariable, neigh, problem))
{
if (!valuesToPrune.Any(v => v == valPruned))
{
valuesToPrune.Add(valPruned);
}
}
//Remove the value from the variable domain in temporal CSP and add to the domain prune
foreach (var prunedVal in valuesToPrune)
{
//Remove domain from variable in problem
problem.RemoveDomainElementFromVariable(neigh, prunedVal);
//remove domain from variable in current variable
neigh.removeDomainElement(prunedVal);
if (!neigh.remDomain.Any())
{
return(false);
}
//Add prune action to assignment
assign.AddDomainPrune(neigh.pos, prunedVal);
}
if (valuesToPrune.Any())
{
queueToPrune.Add(neigh);
}
}
}
return(true);
}
private static List <OverFloorType> MAC3HeadTailChecker(Variable headVar, Variable tailVar, CSP problem)
{
var ret = new List <OverFloorType>();
//Loop remaining domain values
var remainingDomains = tailVar.remDomain.ToList();
foreach (var remDomTail in remainingDomains)
{
int validTailValue = 0;
problem.AssignValue(tailVar, remDomTail, false);
var remDomainHead = headVar.remDomain.ToList();
foreach (var remDomHead in remDomainHead)
{
var alreadyAssigned = problem.IsVariableAssigned(headVar);
if (!alreadyAssigned)
{
problem.AssignValue(headVar, remDomHead, false);
}
bool valid = problem.ValidateConstraints();
if (!valid)
{
validTailValue++;
break;
}
if (!alreadyAssigned)
{
problem.RemoveValue(headVar);
}
}
if (validTailValue == remDomainHead.Count())
{
ret.Add(remDomTail);
}
problem.RemoveValue(tailVar);
}
return(ret);
}
/// <summary>
/// Loop all variables and values searching for a solution for the CSP
/// </summary>
/// <param name="problem"></param>
/// <returns></returns>
public static List <Assignment> RecursiveBacktrackingSearch(CSP problem)
{
if (problem.Goal())
{
Debug.Log("Goal completed!");
return(problem.GetAssignments());
}
//Loop unassigned
var orderedVars = problem.OrderVariablesByMinimumRemainingValues();
foreach (var variable in orderedVars)
{
Debug.Log("Variable evaluated:" + variable.pos.ToString());
var orderedAssignments = problem.OrderAssignmentsByLeastRestrictingValues(variable);
foreach (var assign in orderedAssignments)
{
Debug.Log("Value evaluated:" + assign.value.ToString());
//Assign value
bool validResult = problem.AssignValue(assign.variable, assign.value);
if (!validResult)
{
throw new Exception("Error getting available values");
}
List <Assignment> validAssignments = null;
validAssignments = RecursiveBacktrackingSearch(new CSP(problem));
if (validAssignments != null)
{
return(validAssignments);
}
else
{
Debug.Log("Backtracking value:" + assign.value.ToString());
problem.RemoveValue(assign.variable);
}
}
}
Debug.Log("Backtracking");
return(null);
}
private static List<OverFloorType> MAC3HeadTailChecker(Variable headVar, Variable tailVar, CSP problem)
{
var ret = new List<OverFloorType>();
//Loop remaining domain values
var remainingDomains = tailVar.remDomain.ToList();
foreach (var remDomTail in remainingDomains)
{
int validTailValue = 0;
problem.AssignValue(tailVar, remDomTail, false);
var remDomainHead = headVar.remDomain.ToList();
foreach (var remDomHead in remDomainHead)
{
var alreadyAssigned = problem.IsVariableAssigned(headVar);
if(!alreadyAssigned)problem.AssignValue(headVar, remDomHead, false);
bool valid = problem.ValidateConstraints();
if (!valid)
{
validTailValue++;
break;
}
if (!alreadyAssigned) problem.RemoveValue(headVar);
}
if (validTailValue == remDomainHead.Count())
ret.Add(remDomTail);
problem.RemoveValue(tailVar);
}
return ret;
}
/// <summary>
/// Loop all variables and values searching for a solution for the CSP
/// </summary>
/// <param name="problem"></param>
/// <returns></returns>
public static List<Assignment> RecursiveBacktrackingSearch(CSP problem)
{
if (problem.Goal())
{
Debug.Log("Goal completed!");
return problem.GetAssignments();
}
//Loop unassigned
var orderedVars = problem.OrderVariablesByMinimumRemainingValues();
foreach (var variable in orderedVars)
{
Debug.Log("Variable evaluated:" + variable.pos.ToString());
var orderedAssignments = problem.OrderAssignmentsByLeastRestrictingValues(variable);
foreach (var assign in orderedAssignments)
{
Debug.Log("Value evaluated:" + assign.value.ToString());
//Assign value
bool validResult = problem.AssignValue(assign.variable, assign.value);
if (!validResult)
throw new Exception("Error getting available values");
List<Assignment> validAssignments = null;
validAssignments = RecursiveBacktrackingSearch(new CSP(problem));
if (validAssignments != null)
{
return validAssignments;
}
else
{
Debug.Log("Backtracking value:" + assign.value.ToString());
problem.RemoveValue(assign.variable);
}
}
}
Debug.Log("Backtracking");
return null;
}
/// <summary>
/// Maintenance Arc Consistency, this algorithm will check how many domain prunes are done when a assignemnt is executed
/// </summary>
/// <param name="assign">Assignment to be evaluated and updated</param>
/// <param name="neighbours">List of neighbours to start with (difference between AC3 and MAC3)</param>
/// <returns></returns>
public static bool MAC3(ref Assignment assign,CSP problem)
{
var position = assign.variable.pos;
var variableInLocalProblem = problem.vars.First(v => v.pos == position);
//Add the assignment to the problem
problem.AssignValue(variableInLocalProblem, assign.value,false);
List<Variable> queueToPrune = new List<Variable>();
queueToPrune.Add(variableInLocalProblem);
while (queueToPrune.Any())
{
//Get the first variable
var headVariable = queueToPrune.First();
queueToPrune.Remove(headVariable);
//Get the neighbours of the variable
List<Variable> neighbours = problem.GetNeighbours(headVariable).Where(n => !problem.IsVariableAssigned(n)).ToList();
//Loop over neighbours
foreach (var neigh in neighbours)
{
//Get the list of values to delete for conflict
List<OverFloorType> valuesToPrune = new List<OverFloorType>();
//Check if value is compatible with remaining values in head
foreach (var valPruned in MAC3HeadTailChecker(headVariable, neigh, problem))
{
if (!valuesToPrune.Any(v => v == valPruned))
valuesToPrune.Add(valPruned);
}
//Remove the value from the variable domain in temporal CSP and add to the domain prune
foreach (var prunedVal in valuesToPrune)
{
//Remove domain from variable in problem
problem.RemoveDomainElementFromVariable(neigh, prunedVal);
//remove domain from variable in current variable
neigh.removeDomainElement(prunedVal);
if (!neigh.remDomain.Any())
return false;
//Add prune action to assignment
assign.AddDomainPrune(neigh.pos, prunedVal);
}
if (valuesToPrune.Any())
{
queueToPrune.Add(neigh);
}
}
}
return true;
}
