aima.core.environment.wumpusworld

Class HybridWumpusAgent

java.lang.Object

aima.core.agent.impl.AbstractAgent

aima.core.environment.wumpusworld.HybridWumpusAgent

All Implemented Interfaces:

Agent, EnvironmentObject

public class HybridWumpusAgent
extends AbstractAgent

Artificial Intelligence A Modern Approach (3rd Edition): page 270.

 
 function HYBRID-WUMPUS-AGENT(percept) returns an action
   inputs: percept, a list, [stench, breeze, glitter, bump, scream]
   persistent: KB, a knowledge base, initially the atemporal "wumpus physics"
               t, a counter, initially 0, indicating time
               plan, an action sequence, initially empty
 
   TELL(KB, MAKE-PERCEPT-SENTENCE(percept, t))
   TELL the KB the temporal "physics" sentences for time t
   safe <- {[x, y] : ASK(KB, OKtx,y) = true}
   if ASK(KB, Glittert) = true then
      plan <- [Grab] + PLAN-ROUTE(current, {[1,1]}, safe) + [Climb]
   if plan is empty then
      unvisited <- {[x, y] : ASK(KB, Lt'x,y) = false for all t' ≤ t}
      plan <- PLAN-ROUTE(current, unvisited ∩ safe, safe)
   if plan is empty and ASK(KB, HaveArrowt) = true then
      possible_wumpus <- {[x, y] : ASK(KB, ~Wx,y) = false}
      plan <- PLAN-SHOT(current, possible_wumpus, safe)
   if plan is empty then //no choice but to take a risk
      not_unsafe <- {[x, y] : ASK(KB, ~OKtx,y) = false}
      plan <- PLAN-ROUTE(current, unvisited ∩ not_unsafe, safe)
   if plan is empty then
      plan <- PLAN-ROUTE(current, {[1,1]}, safe) + [Climb]
   action <- POP(plan)
   TELL(KB, MAKE-ACTION-SENTENCE(action, t))
   t <- t+1
   return action
 
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 function PLAN-ROUTE(current, goals, allowed) returns an action sequence
   inputs: current, the agent's current position
           goals, a set of squares; try to plan a route to one of them
           allowed, a set of squares that can form part of the route 
    
   problem <- ROUTE-PROBLEM(current, goals, allowed)
   return A*-GRAPH-SEARCH(problem)
 
 

Figure 7.20 A hybrid agent program for the wumpus world. It uses a propositional knowledge base to infer the state of the world, and a combination of problem-solving search and domain-specific code to decide what actions to take

Author:

Federico Baron, Alessandro Daniele, Ciaran O'Reilly

Field Summary

Fields inherited from class aima.core.agent.impl.AbstractAgent

program

Constructor Summary

Constructors

Constructor and Description
HybridWumpusAgent()
HybridWumpusAgent(int caveXandYDimensions)

Method Summary

Modifier and Type	Method and Description
Action	execute(Percept percept) function HYBRID-WUMPUS-AGENT(percept) returns an action
java.util.List<Action>	planRoute(AgentPosition current, java.util.Set<Room> goals, java.util.Set<Room> allowed) Returns a sequence of actions using A* Search.
java.util.List<Action>	planShot(AgentPosition current, java.util.Set<Room> possibleWumpus, java.util.Set<Room> allowed)

Methods inherited from class aima.core.agent.impl.AbstractAgent

isAlive, setAlive

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HybridWumpusAgent

public HybridWumpusAgent()

HybridWumpusAgent

public HybridWumpusAgent(int caveXandYDimensions)

Method Detail

execute

public Action execute(Percept percept)

function HYBRID-WUMPUS-AGENT(percept) returns an action

Specified by:

execute in interface Agent

Overrides:

execute in class AbstractAgent

Parameters:

percept - a list, [stench, breeze, glitter, bump, scream]

Returns:

an action the agent should take.

planRoute

public java.util.List<Action> planRoute(AgentPosition current,
                                        java.util.Set<Room> goals,
                                        java.util.Set<Room> allowed)

Returns a sequence of actions using A* Search.

Parameters:

current - the agent's current position

goals - a set of squares; try to plan a route to one of them

allowed - a set of squares that can form part of the route

Returns:

the best sequence of actions that the agent have to do to reach a goal from the current position.

planShot

public java.util.List<Action> planShot(AgentPosition current,
                                       java.util.Set<Room> possibleWumpus,
                                       java.util.Set<Room> allowed)

Parameters:

current - the agent's current position

possibleWumpus - a set of squares where we don't know that there isn't the wumpus.

allowed - a set of squares that can form part of the route

Returns:

the sequence of actions to reach the nearest square that is in line with a possible wumpus position. The last action is a shot.