/// <summary>
/// Computes the forward cost heuristics for the given state in the relaxed planning graph.
/// </summary>
/// <param name="state">Starting state.</param>
/// <param name="goalConditions">Goal conditions.</param>
/// <param name="evaluationStrategy">Evaluation strategy.</param>
/// <returns>Forward cost heuristic value from the specified state.</returns>
private double ComputeForwardCost(IState state, IConditions goalConditions, ForwardCostEvaluationStrategy evaluationStrategy)
{
IStateLayer previousStateLayer = null;
IStateLayer stateLayer = CreateLabeledStateLayer(state.GetRelaxedState());
ActionLayer actionLayer = new ActionLayer();
while (!stateLayer.Equals(previousStateLayer))
{
// check goal conditions
if (goalConditions.Evaluate(stateLayer.GetState()))
{
return(goalConditions.EvaluateOperatorPlanningGraphLabel(stateLayer.GetStateLabels(), evaluationStrategy));
}
// build new action layer
actionLayer.Clear();
foreach (var successor in RelaxedProblem.GetSuccessors(stateLayer.GetState()))
{
IOperator appliedOperator = successor.GetAppliedOperator();
double label = appliedOperator.ComputePlanningGraphLabel(stateLayer.GetStateLabels(), evaluationStrategy);
actionLayer.Add(new ActionNode(appliedOperator, label + appliedOperator.GetCost()));
}
// build new state layer
previousStateLayer = stateLayer;
stateLayer = CreateLabeledStateLayer(stateLayer, actionLayer);
}
// failure, solution cannot be found from the specified state
return(int.MaxValue);
}
