/**
* Clears the set of explored states and calls the search implementation of
* <code>QueSearch</code>
*/
public override List<Action> search(Problem problem, Queue<Node> frontier)
{
// Initialize the explored set to be empty
explored.Clear();
frontierStates.Clear();
return base.search(problem, frontier);
}
/**
* Clears the set of explored states and calls the search implementation of
* <code>QueSearch</code>
*/
public override List<Action> search(Problem problem, Queue<Node> frontier)
{
// initialize the explored set to be empty
explored.Clear();
// expandedNodes = new List<Node>();
return base.search(problem, frontier);
}
public BidirectionalEightPuzzleProblem(EightPuzzleBoard initialState)
: base(initialState, EightPuzzleFunctionFactory.getActionsFunction(),
EightPuzzleFunctionFactory.getResultFunction(),
new DefaultGoalTest(new EightPuzzleBoard(new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8 })))
{
reverseProblem = new Problem(new EightPuzzleBoard(new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8 }),
EightPuzzleFunctionFactory.getActionsFunction(), EightPuzzleFunctionFactory.getResultFunction(),
new DefaultGoalTest(initialState));
}
/**
* Calls the goal test of the problem and - if the goal test is effectively
* a {@link SolutionChecker} - additionally checks, whether the solution is
* acceptable. Solution checkers can be used to analyze several or all
* solutions with only one search run.
*/
public static bool isGoalState(Problem p, Node n)
{
bool isGoal = false;
GoalTest gt = p.getGoalTest();
if (gt.isGoalState(n.getState()))
{
if (gt is SolutionChecker)
{
isGoal = ((SolutionChecker)gt).isAcceptableSolution(
getSequenceOfActions(n), n.getState());
}
else
{
isGoal = true;
}
}
return isGoal;
}
/**
* Returns the children obtained from expanding the specified node in the
* specified problem.
*
* @param node
* the node to expand
* @param problem
* the problem the specified node is within.
*
* @return the children obtained from expanding the specified node in the
* specified problem.
*/
public List<Node> expand(Node node, Problem problem)
{
List<Node> successors = new List<Node>();
ActionsFunction actionsFunction = problem.getActionsFunction();
ResultFunction resultFunction = problem.getResultFunction();
StepCostFunction stepCostFunction = problem.getStepCostFunction();
foreach (Action action in actionsFunction.actions(node.getState()))
{
System.Object successorState = resultFunction.result(node.getState(), action);
double stepCost = stepCostFunction.c(node.getState(), action, successorState);
successors.Add(createNode(successorState, node, action, stepCost));
}
foreach (NodeListener listener in nodeListeners)
{
listener.onNodeExpanded(node);
}
counter++;
return successors;
}
public SearchAgent(Problem p, Search search)
{
actionList = search.search(p);
actionIterator = actionList.GetEnumerator();
searchMetrics = search.getMetrics();
}
protected abstract List<Action> search(Problem problem);
/**
* Returns a list of actions to the goal if the goal was found, a list
* containing a single NoOp Action if already at the goal, or an empty list
* if the goal could not be found. This template method provides a base for
* tree and graph search implementations. It can be customized by overriding
* some primitive operations, especially {@link #addToFrontier(Node)},
* {@link #removeFromFrontier()}, and {@link #isFrontierEmpty()}.
*
* @param problem
* the search problem
* @param frontier
* the collection of nodes that are waiting to be expanded
*
* @return a list of actions to the goal if the goal was found, a list
* containing a single NoOp Action if already at the goal, or an
* empty list if the goal could not be found.
*/
public virtual List<Action> search(Problem problem, Queue<Node> frontier)
{
this.frontier = frontier;
clearInstrumentation();
// initialize the frontier using the initial state of the problem
Node root = nodeExpander.createRootNode(problem.getInitialState());
if (earlyGoalCheck)
{
if(SearchUtils.isGoalState(problem, root))
{
return getSolution(root);
}
}
addToFrontier(root);
while(!(frontier.Count == 0))
{
// choose a leaf node and remove it from the frontier
Node nodeToExpand = removeFromFrontier();
// Only need to check the nodeToExpand if have not already
// checked before adding to the frontier
if (!earlyGoalCheck)
{
// if the node contains a goal state then return the
// corresponding solution
if(SearchUtils.isGoalState(problem, nodeToExpand))
{
return getSolution(nodeToExpand);
}
}
// expand the chosen node, adding the resulting nodes to the
// frontier
foreach(Node successor in nodeExpander.expand(nodeToExpand, problem))
{
if (earlyGoalCheck)
{
if(SearchUtils.isGoalState(problem, successor))
{
return getSolution(successor);
}
}
addToFrontier(successor)
; }
}
// if the frontier is empty then return failure
return SearchUtils.failure();
}
