82 lines
3.0 KiB
Python
82 lines
3.0 KiB
Python
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# ghostAgents.py
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# --------------
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# Licensing Information: You are free to use or extend these projects for
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# educational purposes provided that (1) you do not distribute or publish
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# solutions, (2) you retain this notice, and (3) you provide clear
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# attribution to UC Berkeley, including a link to http://ai.berkeley.edu.
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#
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# Attribution Information: The Pacman AI projects were developed at UC Berkeley.
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# The core projects and autograders were primarily created by John DeNero
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# (denero@cs.berkeley.edu) and Dan Klein (klein@cs.berkeley.edu).
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# Student side autograding was added by Brad Miller, Nick Hay, and
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# Pieter Abbeel (pabbeel@cs.berkeley.edu).
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from game import Agent
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from game import Actions
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from game import Directions
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import random
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from util import manhattanDistance
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import util
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class GhostAgent( Agent ):
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def __init__( self, index ):
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self.index = index
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def getAction( self, state ):
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dist = self.getDistribution(state)
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if len(dist) == 0:
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return Directions.STOP
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else:
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return util.chooseFromDistribution( dist )
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def getDistribution(self, state):
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"Returns a Counter encoding a distribution over actions from the provided state."
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util.raiseNotDefined()
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class RandomGhost( GhostAgent ):
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"A ghost that chooses a legal action uniformly at random."
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def getDistribution( self, state ):
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dist = util.Counter()
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for a in state.getLegalActions( self.index ): dist[a] = 1.0
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dist.normalize()
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return dist
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class DirectionalGhost( GhostAgent ):
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"A ghost that prefers to rush Pacman, or flee when scared."
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def __init__( self, index, prob_attack=0.8, prob_scaredFlee=0.8 ):
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self.index = index
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self.prob_attack = prob_attack
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self.prob_scaredFlee = prob_scaredFlee
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def getDistribution( self, state ):
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# Read variables from state
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ghostState = state.getGhostState( self.index )
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legalActions = state.getLegalActions( self.index )
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pos = state.getGhostPosition( self.index )
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isScared = ghostState.scaredTimer > 0
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speed = 1
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if isScared: speed = 0.5
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actionVectors = [Actions.directionToVector( a, speed ) for a in legalActions]
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newPositions = [( pos[0]+a[0], pos[1]+a[1] ) for a in actionVectors]
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pacmanPosition = state.getPacmanPosition()
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# Select best actions given the state
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distancesToPacman = [manhattanDistance( pos, pacmanPosition ) for pos in newPositions]
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if isScared:
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bestScore = max( distancesToPacman )
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bestProb = self.prob_scaredFlee
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else:
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bestScore = min( distancesToPacman )
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bestProb = self.prob_attack
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bestActions = [action for action, distance in zip( legalActions, distancesToPacman ) if distance == bestScore]
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# Construct distribution
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dist = util.Counter()
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for a in bestActions: dist[a] = bestProb / len(bestActions)
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for a in legalActions: dist[a] += ( 1-bestProb ) / len(legalActions)
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dist.normalize()
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return dist
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