// function HILL-CLIMBING(problem) returns a state that is a local maximum
public List<Action> search(Problem p) {
clearInstrumentation();
outcome = SearchOutcome.FAILURE;
lastState = null;
// current <- MAKE-NODE(problem.INITIAL-STATE)
Node current = new Node(p.getInitialState());
Node neighbor = null;
// loop do
while (!CancelableThread.currIsCanceled()) {
List<Node> children = expandNode(current, p);
// neighbor <- a highest-valued successor of current
neighbor = getHighestValuedNodeFrom(children, p);
// if neighbor.VALUE <= current.VALUE then return current.STATE
if ((neighbor == null) || (getValue(neighbor) <= getValue(current))) {
if (SearchUtils.isGoalState(p, current)) {
outcome = SearchOutcome.SOLUTION_FOUND;
}
lastState = current.getState();
return SearchUtils.actionsFromNodes(current.getPathFromRoot());
}
// current <- neighbor
current = neighbor;
}
return new List<Action>();
}
/**
*
* @param problem
* @param frontier
* @return if goal found, the list of actions to the Goal. If already at the
* goal you will receive a List with a single NoOp Action in it. If
* fail to find the Goal, an empty list will be returned to indicate
* that the search failed.
*/
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 = new Node(problem.getInitialState());
if (isCheckGoalBeforeAddingToFrontier())
{
if (SearchUtils.isGoalState(problem, root))
{
return(SearchUtils.actionsFromNodes(root.getPathFromRoot()));
}
}
frontier.Enqueue(root);
setQueueSize(frontier.Count);
while (!(frontier.Count == 0))
{
// choose a leaf node and remove it from the frontier
Node nodeToExpand = popNodeFromFrontier();
setQueueSize(frontier.Count);
// Only need to check the nodeToExpand if have not already
// checked before adding to the frontier
if (!isCheckGoalBeforeAddingToFrontier())
{
// if the node contains a goal state then return the
// corresponding solution
if (SearchUtils.isGoalState(problem, nodeToExpand))
{
setPathCost(nodeToExpand.getPathCost());
return(SearchUtils.actionsFromNodes(nodeToExpand
.getPathFromRoot()));
}
}
// expand the chosen node, adding the resulting nodes to the
// frontier
foreach (Node fn in getResultingNodesToAddToFrontier(nodeToExpand,
problem))
{
if (isCheckGoalBeforeAddingToFrontier())
{
if (SearchUtils.isGoalState(problem, fn))
{
setPathCost(fn.getPathCost());
return(SearchUtils.actionsFromNodes(fn
.getPathFromRoot()));
}
}
frontier.Enqueue(fn);
}
setQueueSize(frontier.Count);
}
// if the frontier is empty then return failure
return(failure());
}
public void testGetPathFromRoot()
{
Node node1 = new Node("state1");
Node node2 = new Node("state2", node1, null, 1.0);
Node node3 = new Node("state3", node2, null, 1.0);
List<Node> path = node3.getPathFromRoot();
Assert.Equals(node1, path[0]);
Assert.Equals(node2, path[1]);
Assert.Equals(node3, path[2]);
}
/**
*
* @param problem
* @param frontier
* @return if goal found, the list of actions to the Goal. If already at the
* goal you will receive a List with a single NoOp Action in it. If
* fail to find the Goal, an empty list will be returned to indicate
* that the search failed.
*/
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 = new Node(problem.getInitialState());
if (isCheckGoalBeforeAddingToFrontier())
{
if (SearchUtils.isGoalState(problem, root))
{
return SearchUtils.actionsFromNodes(root.getPathFromRoot());
}
}
frontier.Enqueue(root);
setQueueSize(frontier.Count);
while (!(frontier.Count==0))
{
// choose a leaf node and remove it from the frontier
Node nodeToExpand = popNodeFromFrontier();
setQueueSize(frontier.Count);
// Only need to check the nodeToExpand if have not already
// checked before adding to the frontier
if (!isCheckGoalBeforeAddingToFrontier())
{
// if the node contains a goal state then return the
// corresponding solution
if (SearchUtils.isGoalState(problem, nodeToExpand))
{
setPathCost(nodeToExpand.getPathCost());
return SearchUtils.actionsFromNodes(nodeToExpand
.getPathFromRoot());
}
}
// expand the chosen node, adding the resulting nodes to the
// frontier
foreach (Node fn in getResultingNodesToAddToFrontier(nodeToExpand,
problem))
{
if (isCheckGoalBeforeAddingToFrontier())
{
if (SearchUtils.isGoalState(problem, fn))
{
setPathCost(fn.getPathCost());
return SearchUtils.actionsFromNodes(fn
.getPathFromRoot());
}
}
frontier.Enqueue(fn);
}
setQueueSize(frontier.Count);
}
// if the frontier is empty then return failure
return failure();
}
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(
SearchUtils.actionsFromNodes(n.getPathFromRoot()), n
.getState());
}
else
{
isGoal = true;
}
}
return isGoal;
}
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(
SearchUtils.actionsFromNodes(n.getPathFromRoot()), n
.getState());
}
else
{
isGoal = true;
}
}
return(isGoal);
}
// function SIMULATED-ANNEALING(problem, schedule) returns a solution state
public List<Action> search(Problem p) {
clearInstrumentation();
outcome = SearchOutcome.FAILURE;
lastState = null;
// current <- MAKE-NODE(problem.INITIAL-STATE)
Node current = new Node(p.getInitialState());
Node next = null;
List<Action> ret = new List<Action>();
// for t = 1 to INFINITY do
int timeStep = 0;
while (!CancelableThread.currIsCanceled()) {
// temperature <- schedule(t)
double temperature = scheduler.getTemp(timeStep);
timeStep++;
// if temperature = 0 then return current
if (temperature == 0.0) {
if (SearchUtils.isGoalState(p, current)) {
outcome = SearchOutcome.SOLUTION_FOUND;
}
ret = SearchUtils.actionsFromNodes(current.getPathFromRoot());
lastState = current.getState();
break;
}
List<Node> children = expandNode(current, p);
if (children.Count > 0) {
// next <- a randomly selected successor of current
next = Util.selectRandomlyFromList(children);
// /\E <- next.VALUE - current.value
double deltaE = getValue(p, next) - getValue(p, current);
if (shouldAccept(temperature, deltaE)) {
current = next;
}
}
}
return ret;
}
//
// PRIVATE METHODS
//
// function RECURSIVE-DLS(node, problem, limit) returns a solution, or
// failure/cutoff
private List<Action> recursiveDLS(Node node, Problem problem, int limit)
{
// if problem.GOAL-TEST(node.STATE) then return SOLUTION(node)
if (SearchUtils.isGoalState(problem, node))
{
setPathCost(node.getPathCost());
return SearchUtils.actionsFromNodes(node.getPathFromRoot());
}
else if (0 == limit)
{
// else if limit = 0 then return cutoff
return cutoff();
}
else
{
// else
// cutoff_occurred? <- false
bool cutoff_occurred = false;
// for each action in problem.ACTIONS(node.STATE) do
foreach (Node child in this.expandNode(node, problem))
{
// child <- CHILD-NODE(problem, node, action)
// result <- RECURSIVE-DLS(child, problem, limit - 1)
List<Action> result = recursiveDLS(child, problem, limit - 1);
// if result = cutoff then cutoff_occurred? <- true
if (isCutOff(result))
{
cutoff_occurred = true;
}
else if (!isFailure(result))
{
// else if result != failure then return result
return result;
}
}
// if cutoff_occurred? then return cutoff else return failure
if (cutoff_occurred)
{
return cutoff();
}
else
{
return failure();
}
}
}
