private double getValue(Node n) {
// assumption greater heuristic value =>
// HIGHER on hill; 0 == goal state;
return -1 * hf.h(n.getState());
}
// 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>();
}
public override Node popNodeFromFrontier()
{
Node toRemove = base.popNodeFromFrontier();
frontierState.Remove(toRemove.getState());
return(toRemove);
}
public override bool removeNodeFromFrontier(Node toRemove)
{
bool removed = base.removeNodeFromFrontier(toRemove);
if (removed)
{
frontierState.Remove(toRemove.getState());
}
return removed;
}
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 override bool removeNodeFromFrontier(Node toRemove)
{
bool removed = base.removeNodeFromFrontier(toRemove);
if (removed)
{
frontierState.Remove(toRemove.getState());
}
return(removed);
}
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 List <Node> expandNode(Node node, Problem problem)
{
List <Node> childNodes = 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);
childNodes.Add(new Node(successorState, node, action, stepCost));
}
metrics.set(METRIC_NODES_EXPANDED, metrics
.getInt(METRIC_NODES_EXPANDED) + 1);
return(childNodes);
}
public List<Node> expandNode(Node node, Problem problem)
{
List<Node> childNodes = 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);
childNodes.Add(new Node(successorState, node, action, stepCost));
}
metrics.set(METRIC_NODES_EXPANDED, metrics
.getInt(METRIC_NODES_EXPANDED) + 1);
return childNodes;
}
public override List<Node> getResultingNodesToAddToFrontier(Node nodeToExpand,
Problem problem)
{
addToFrontier.Clear();
// add the node to the explored set
explored.Add(nodeToExpand.getState());
// expand the chosen node, adding the resulting nodes to the frontier
foreach (Node cfn in expandNode(nodeToExpand, problem))
{
Node frontierNode = frontierState[cfn.getState()];
bool yesAddToFrontier = false;
// only if not in the frontier or explored set
if (null == frontierNode && !explored.Contains(cfn.getState()))
{
yesAddToFrontier = true;
}
else if (null != frontierNode
&& null != replaceFrontierNodeAtStateCostFunction
&& replaceFrontierNodeAtStateCostFunction.Compare(cfn,
frontierNode) < 0)
{
// child.STATE is in frontier with higher cost
// replace that frontier node with child
yesAddToFrontier = true;
// Want to replace the current frontier node with the child
// node therefore mark the child to be added and remove the
// current fontierNode
removeNodeFromFrontier(frontierNode);
// Ensure removed from add to frontier as well
// as 1 or more may reach the same state at the same time
addToFrontier.Remove(frontierNode);
}
if (yesAddToFrontier)
{
addToFrontier.Add(cfn);
frontierState.Add(cfn.getState(), cfn);
}
}
return addToFrontier;
}
public override List <Node> getResultingNodesToAddToFrontier(Node nodeToExpand,
Problem problem)
{
addToFrontier.Clear();
// add the node to the explored set
explored.Add(nodeToExpand.getState());
// expand the chosen node, adding the resulting nodes to the frontier
foreach (Node cfn in expandNode(nodeToExpand, problem))
{
Node frontierNode = frontierState[cfn.getState()];
bool yesAddToFrontier = false;
// only if not in the frontier or explored set
if (null == frontierNode && !explored.Contains(cfn.getState()))
{
yesAddToFrontier = true;
}
else if (null != frontierNode &&
null != replaceFrontierNodeAtStateCostFunction &&
replaceFrontierNodeAtStateCostFunction.Compare(cfn,
frontierNode) < 0)
{
// child.STATE is in frontier with higher cost
// replace that frontier node with child
yesAddToFrontier = true;
// Want to replace the current frontier node with the child
// node therefore mark the child to be added and remove the
// current fontierNode
removeNodeFromFrontier(frontierNode);
// Ensure removed from add to frontier as well
// as 1 or more may reach the same state at the same time
addToFrontier.Remove(frontierNode);
}
if (yesAddToFrontier)
{
addToFrontier.Add(cfn);
frontierState.Add(cfn.getState(), cfn);
}
}
return(addToFrontier);
}
// 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 double getValue(Problem p, Node n) {
// assumption greater heuristic value =>
// HIGHER on hill; 0 == goal state;
// SA deals with gardient DESCENT
return -1 * hf.h(n.getState());
}
public double f(Node n)
{
// f(n) = h(n)
return hf.h(n.getState());
}
public double f(Node n)
{
// f(n) = g(n) + h(n)
return gf.g(n) + hf.h(n.getState());
}
