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===== *. aima.search.online.LRTAStarAgent - Initial implementation of algorithm in Fig 4.23. *. aima.test.search.online.LRTAStarAgentTest - Test case for LRTAStarAgent - Note: One test currently commented out as algorithm goes into eternal loop based on the condition it is testing. *. aima.search.online.ActionState - Factored out code from OnlineDFSAgent for re-use in LRTAStarAgent Modified ======== *. aima.search.online.OnlineDFSAgent - Factored out ActionState for re-use in LRTAStarAgent. *. aima.test.learningtest.neural.BackPropagationTests - Commented out System.outs *. aim.test.search.SearchTests - Added LRTAStarAgentTest to suite.
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‎src/aima/search/online/ActionState.java‎

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package aima.search.online;
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import aima.basic.Percept;
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public class ActionState {
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private final Object action;
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private final Percept state;
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public ActionState(Object action, Percept state) {
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this.action = action;
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this.state = state;
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}
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public Object getAction() {
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return action;
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}
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public Percept getState() {
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return state;
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}
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@Override
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public boolean equals(Object o) {
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if (o == null || !(o instanceof ActionState)) {
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return super.equals(o);
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}
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return (action.equals(((ActionState) o).action) && state
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.equals(((ActionState) o).state));
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}
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@Override
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public int hashCode() {
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return action.hashCode() + state.hashCode();
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}
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@Override
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public String toString() {
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return "(" + action + ", " + state + ")";
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}
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}

‎src/aima/search/online/LRTAStarAgent.java‎

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package aima.search.online;
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import java.util.ArrayList;
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import java.util.Hashtable;
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import java.util.List;
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import aima.basic.Agent;
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import aima.basic.Percept;
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import aima.search.framework.Problem;
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import aima.search.framework.Successor;
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/**
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* Artificial Intelligence A Modern Approach (2nd Edition): Figure 4.23, page
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* 128.<br>
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* <code>
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* function LRTA*AGENT(s') returns an action
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* inputs: s', a percept that identifies the current state
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* static: result, a table, indexed by action and state, initially empty
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* H, a table of cost estimates indexed by state, initially empty
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* s, a, the previous state and action, initially null
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*
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* if GOAL-TEST(s') then return stop
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* if s' is new state (not in H) then H[s'] <- h(s')
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* unless s is null
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* result[a, s] <- s'
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* H[s] <- min LRTA*-COST(s, b, result[b, s], H)
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* b (element of) ACTIONS(s)
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* a <- an action b in ACTIONS(s') that minimizes LRTA*-COST(s', b, result[b, s'], H)
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* s <- s'
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* return a
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*
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*
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* function LRTA*-COST(s, a, s', H) returns a cost estimate
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* if s' is undefined then return h(s)
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* else return c(s, a, s') + H[s']
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* </code>
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*
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* Figure 4.23 LRTA*-AGENT selects an action according to the value of
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* neighboring states, which are updated as the agent moves about the state
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* space.<br>
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* Note: This algorithm fails to exit if the goal does not exist (e.g. A<->B Goal=X),
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* this could be an issue with the implementation. Comments welcome.
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*/
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/**
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* @author Ciaran O'Reilly
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*
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*/
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public class LRTAStarAgent extends Agent {
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private Problem problem;
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// static: result, a table, indexed by action and state, initially empty
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private final Hashtable<ActionState, Percept> result = new Hashtable<ActionState, Percept>();
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// H, a table of cost estimates indexed by state, initially empty
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private final Hashtable<Percept, Double> H = new Hashtable<Percept, Double>();
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// s, a, the previous state and action, initially null
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private Percept s = null;
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private Object a = null;
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public LRTAStarAgent(Problem problem) {
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setProblem(problem);
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}
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public Problem getProblem() {
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return problem;
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}
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public void setProblem(Problem problem) {
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this.problem = problem;
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init();
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}
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// function LRTA*AGENT(s') returns an action
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// inputs: s', a percept that identifies the current state
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@Override
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public String execute(Percept sComma) {
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// if GOAL-TEST(s') then return stop
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if (!goalTest(sComma)) {
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// if s' is new state (not in H) then H[s'] <- h(s')
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if (!H.containsKey(sComma)) {
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H.put(sComma, getProblem().getHeuristicFunction()
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.getHeuristicValue(sComma));
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}
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// unless s is null
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if (null != s) {
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// result[a, s] <- s'
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result.put(new ActionState(a, s), sComma);
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// H[s] <- min LRTA*-COST(s, b, result[b, s], H)
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// b (element of) ACTIONS(s)
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double min = Double.MAX_VALUE;
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for (Object b : actions(s)) {
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double cost = lrtaCost(s, b, result.get(new ActionState(b,
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s)));
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if (cost < min) {
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min = cost;
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}
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}
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H.put(s, min);
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}
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// a <- an action b in ACTIONS(s') that minimizes LRTA*-COST(s', b,
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// result[b, s'], H)
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double min = Double.MAX_VALUE;
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// Just in case no actions
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a = Agent.NO_OP;
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for (Object b : actions(sComma)) {
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double cost = lrtaCost(sComma, b, result.get(new ActionState(b,
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sComma)));
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if (cost < min) {
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min = cost;
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a = b;
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}
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}
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} else {
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a = Agent.NO_OP;
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}
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// s <- s'
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s = sComma;
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if (Agent.NO_OP.equals(a)) {
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// I'm either at the Goal or can't get to it,
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// which in either case I'm finished so just die.
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die();
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}
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// return a
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return a.toString();
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}
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//
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// PRIVATE METHODS
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//
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private void init() {
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live();
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result.clear();
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H.clear();
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s = null;
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a = null;
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}
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private boolean goalTest(Percept state) {
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return getProblem().isGoalState(state);
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}
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// function LRTA*-COST(s, a, s', H) returns a cost estimate
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private double lrtaCost(Percept s, Object action, Percept sComma) {
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// if s' is undefined then return h(s)
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if (null == sComma) {
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return getProblem().getHeuristicFunction().getHeuristicValue(s);
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}
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// else return c(s, a, s') + H[s']
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return getProblem().getStepCostFunction().calculateStepCost(s, sComma,
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action.toString())
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+ H.get(sComma);
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}
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private List<Object> actions(Percept state) {
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List<Object> actions = new ArrayList<Object>();
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List<Successor> successors = getProblem().getSuccessorFunction()
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.getSuccessors(state);
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for (Successor s : successors) {
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actions.add(s.getAction());
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}
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return actions;
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}
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}

‎src/aima/search/online/OnlineDFSAgent.java‎

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* unexplored, a table that lists, for each visited state, the actions not yet tried
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* unbacktracked, a table that lists, for each visited state, the backtracks not yet tried
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* s, a, the previous state and action, initially null
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*
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*
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* if GOAL-TEST(s') then return stop
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* if s' is a new state then unexplored[s'] <- ACTIONS(s')
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* if s is not null then do
@@ -106,9 +106,9 @@ public String execute(Percept sComma) {
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Percept popped = unbacktracked.get(sComma).remove(
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unbacktracked.get(sComma).size() - 1);
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for (ActionState as : result.keySet()) {
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if (as.state.equals(sComma)
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if (as.getState().equals(sComma)
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&& result.get(as).equals(popped)) {
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a = as.action;
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a = as.getAction();
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break;
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}
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}
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//
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private void init() {
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live();
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result.clear();
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unexplored.clear();
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unbacktracked.clear();
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return actions;
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}
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private class ActionState {
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private final Object action;
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private final Percept state;
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public ActionState(Object action, Percept state) {
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this.action = action;
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this.state = state;
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}
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@Override
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public boolean equals(Object o) {
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if (o == null || !(o instanceof ActionState)) {
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return super.equals(o);
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}
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return (action.equals(((ActionState) o).action) && state
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.equals(((ActionState) o).state));
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}
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@Override
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public int hashCode() {
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return action.hashCode() + state.hashCode();
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}
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@Override
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public String toString() {
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return "(" + action + ", " + state + ")";
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}
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}
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}

‎src/aima/test/learningtest/neural/BackPropagationTests.java‎

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innds.refreshDataset();
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int[] result = ffnn.testOnDataSet(innds);
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System.out.println(result[0] + " right, " + result[1] + " wrong");
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// System.out.println(result[0] + " right, " + result[1] + " wrong");
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}
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155155
innds.refreshDataset();
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int[] result = perc.testOnDataSet(innds);
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System.out.println(result[0] + " right, " + result[1] + " wrong");
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// System.out.println(result[0] + " right, " + result[1] + " wrong");
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}
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}

‎src/aima/test/search/SearchTests.java‎

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import aima.test.search.nqueens.NQueensFitnessFunctionTest;
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import aima.test.search.nqueens.NQueensGoalTestTest;
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import aima.test.search.nqueens.NQueensSuccessorFunctionTest;
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import aima.test.search.online.LRTAStarAgentTest;
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import aima.test.search.online.OnlineDFSAgentTest;
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import aima.test.search.searches.AStarSearchTest;
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import aima.test.search.searches.BidirectionalSearchTest;
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suite.addTest(new TestSuite(GreedyBestFirstSearchTest.class));
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suite.addTest(new TestSuite(IterativeDeepeningSearchTest.class));
5455
suite.addTest(new TestSuite(LIFOQueueTest.class));
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suite.addTest(new TestSuite(LRTAStarAgentTest.class));
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suite.addTest(new TestSuite(MapAgentTest.class));
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suite.addTest(new TestSuite(MapCSPTest.class));
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suite.addTest(new TestSuite(MapEnvironmentTest.class));

‎src/aima/test/search/online/LRTAStarAgentTest.java‎

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package aima.test.search.online;
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import junit.framework.TestCase;
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import aima.basic.BasicEnvironmentView;
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import aima.search.framework.HeuristicFunction;
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import aima.search.map.BidirectionalMapProblem;
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import aima.search.map.Map;
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import aima.search.map.MapEnvironment;
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import aima.search.online.LRTAStarAgent;
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public class LRTAStarAgentTest extends TestCase {
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Map aMap;
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StringBuffer envChanges;
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HeuristicFunction hf;
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@Override
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public void setUp() {
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aMap = new Map(new String[] { "A", "B", "C", "D", "E", "F" });
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aMap.addBidirectionalLink("A", "B", 4);
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aMap.addBidirectionalLink("B", "C", 4);
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aMap.addBidirectionalLink("C", "D", 4);
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aMap.addBidirectionalLink("D", "E", 4);
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aMap.addBidirectionalLink("E", "F", 4);
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hf = new HeuristicFunction() {
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public double getHeuristicValue(Object state) {
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return 1;
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}
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};
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envChanges = new StringBuffer();
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}
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public void testAlreadyAtGoal() {
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MapEnvironment me = new MapEnvironment(aMap);
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LRTAStarAgent agent = new LRTAStarAgent(new BidirectionalMapProblem(me
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.getMap(), "A", "A", hf));
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me.addAgent(agent, "A");
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me.registerView(new BasicEnvironmentView() {
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@Override
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public void envChanged(String command) {
43+
envChanges.append(command).append("->");
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}
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});
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me.stepUntilNoOp();
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48+
assertEquals("NoOP->", envChanges.toString());
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}
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public void testNormalSearch() {
52+
MapEnvironment me = new MapEnvironment(aMap);
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LRTAStarAgent agent = new LRTAStarAgent(new BidirectionalMapProblem(me
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.getMap(), "A", "F", hf));
55+
me.addAgent(agent, "A");
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me.registerView(new BasicEnvironmentView() {
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@Override
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public void envChanged(String command) {
59+
envChanges.append(command).append("->");
60+
}
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});
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me.stepUntilNoOp();
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assertEquals("B->A->B->C->B->C->D->C->D->E->D->E->F->NoOP->",
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envChanges.toString());
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}
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public void testNoPath() {
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// Note: Will search forever if no path is possible.
70+
// MapEnvironment me = new MapEnvironment(aMap);
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// LRTAStarAgent agent = new LRTAStarAgent(new
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// BidirectionalMapProblem(me
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// .getMap(), "A", "G", hf));
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// me.addAgent(agent, "A");
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// me.registerView(new BasicEnvironmentView() {
76+
// @Override
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// public void envChanged(String command) {
78+
// envChanges.append(command).append("->");
79+
// }
80+
// });
81+
// me.stepUntilNoOp();
82+
//
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// assertEquals("B->A->B->C->B->C->D->C->D->E->D->E->F->NoOP->",
84+
// envChanges.toString());
85+
}
86+
}

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