/// <summary>
/// Initialization of the search procedure. Should be done before every search!
/// </summary>
/// <param name="type">Search type.</param>
protected override void InitSearch(SearchType type)
{
base.InitSearch(type);
ProcessedStatesCount = 0;
SolutionCost = 0.0;
SolutionPlan = new SolutionPlan(Problem.GetInitialNode());
}
/// <summary>
/// Gets the solution plan (i.e. a concrete sequence of applied operators).
/// </summary>
/// <returns>Solution plan.</returns>
public override ISolutionPlan GetSolutionPlan()
{
if (ResultStatus != ResultStatus.SolutionFound)
{
return(null);
}
var predecessor = GetPredecessor(GoalNode);
bool isStatesSpecific = (predecessor != null && predecessor.Item2 == null);
if (isStatesSpecific) // no operators involved
{
SolutionPlanViaStates solution = new SolutionPlanViaStates {
GoalNode
};
while (predecessor != null)
{
solution.Add(predecessor.Item1);
predecessor = GetPredecessor(predecessor.Item1);
}
if (SearchType == SearchType.Forward)
{
solution.Reverse();
}
return(solution);
}
else
{
SolutionPlan solution = new SolutionPlan(Problem.GetInitialNode());
while (predecessor != null)
{
solution.Add(predecessor.Item2);
predecessor = GetPredecessor(predecessor.Item1);
}
if (SearchType == SearchType.Forward)
{
solution.Reverse();
}
return(solution);
}
}
/// <summary>
/// Starts the search procedure.
/// </summary>
/// <param name="type">Type of search.</param>
/// <returns>Result of the search.</returns>
public override ResultStatus Start(SearchType type = SearchType.Forward)
{
InitSearch(type);
List <IOperator> transitionCandidates = new List <IOperator>();
ISearchNode currentNode = GetInitialNode();
while (!Problem.IsGoalNode(currentNode))
{
if (IsTimeLimitExceeded())
{
return(FinishSearch(ResultStatus.TimeLimitExceeded));
}
if (IsMemoryLimitExceeded())
{
return(FinishSearch(ResultStatus.MemoryLimitExceeded));
}
LogSearchStatistics();
transitionCandidates.Clear();
double bestCost = double.MaxValue;
IOperator bestCostOperator;
foreach (var transition in Problem.GetTransitions(currentNode))
{
IOperator appliedOperator = transition.GetAppliedOperator();
ISearchNode node = transition.GetTransitionResult();
double transitionCost = appliedOperator.GetCost() + Heuristic.GetValue(node);
if (transitionCost < bestCost)
{
bestCost = transitionCost;
transitionCandidates.Clear();
transitionCandidates.Add(appliedOperator);
}
else if (transitionCost.Equals(bestCost))
{
transitionCandidates.Add(appliedOperator);
}
}
if (transitionCandidates.Count == 0)
{
return(FinishSearch(ResultStatus.NoSolutionFound)); // dead-end reached
}
else if (transitionCandidates.Count == 1)
{
bestCostOperator = transitionCandidates[0];
}
else
{
bestCostOperator = transitionCandidates[RandomNumberGenerator.Next(transitionCandidates.Count)];
}
SolutionPlan.Add(bestCostOperator);
SolutionCost += bestCostOperator.GetCost();
currentNode = Apply(currentNode, bestCostOperator);
++ProcessedStatesCount;
}
if (SearchType != SearchType.Forward)
{
SolutionPlan.Reverse();
}
return(FinishSearch(ResultStatus.SolutionFound, currentNode));
}