Python util.sample函数代码示例

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given its
        previous position (oldPos) as well as Pacman's current position.

        util.sample(Counter object) is a helper method to generate a sample from
        a belief distribution.
        """
        "*** YOUR CODE HERE ***"

        samples = []
        for parPos in self.parDist:
            newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, parPos))
            samples.append(util.sample(newPosDist))
        self.parDist = samples
        
        return self.getBeliefDistribution()
    
        util.raiseNotDefined()

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given
        its previous position (oldPos) as well as Pacman's current
        position.

        util.sample(Counter object) is a helper method to generate a sample from a
        belief distribution
        """
        "*** YOUR CODE HERE ***"
        #util.raiseNotDefined()
        newParticles = []
        self.newPosDistMemo = util.Counter()
        for oldPos in self.particles:
            if oldPos in self.newPosDistMemo.keys():
                newPosDist = self.newPosDistMemo[oldPos]
            else:
                newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))
                self.newPosDistMemo[oldPos] = newPosDist # memoize for speed
            newParticles.append(util.sample(newPosDist))

        self.particles = newParticles

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given
        its previous position (oldPos) as well as Pacman's current
        position.

        util.sample(Counter object) is a helper method to generate a sample from a
        belief distribution
        """
        "*** YOUR CODE HERE ***"

        #util.raiseNotDefined()
         
        beliefs = self.getBeliefDistribution()

        
        for particle in self.particles:
            oldPos=particle[0]
            newPosDist=self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))
            #update particle based on newPosDist
            particle[0] = util.sample(newPosDist);

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given
        its previous position (oldPos) as well as Pacman's current
        position.

        util.sample(Counter object) is a helper method to generate a sample from a
        belief distribution
        """
        "*** YOUR CODE HERE ***"
        #1) go through each particle
        #2) generate the transition probability distribution at the particle's position
        #3) sample from the distribution to get the new position of the particle
        #4) add the particle to the new list

        #counter = util.Counter()
        newParticles = []
        for particle in self.particles:
            #for oldPos in self.legalPositions:
            newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, particle))
            newParticles.append(util.sample(newPosDist))
        self.particles = newParticles

    def observe(self, observation, gameState):
        """
        Update beliefs based on the given distance observation. Make
        sure to handle the special case where all particles have weight
        0 after reweighting based on observation. If this happens,
        resample particles uniformly at random from the set of legal
        positions (self.legalPositions).

        A correct implementation will handle two special cases:
          1) When a ghost is captured by Pacman, **all** particles should be updated so
             that the ghost appears in its prison cell, self.getJailPosition()

             You can check if a ghost has been captured by Pacman by
             checking if it has a noisyDistance of None (a noisy distance
             of None will be returned if, and only if, the ghost is
             captured).

          2) When all particles receive 0 weight, they should be recreated from the
             prior distribution by calling initializeUniformly. The total weight
             for a belief distribution can be found by calling totalCount on
             a Counter object

        util.sample(Counter object) is a helper method to generate a sample from
        a belief distribution

        You may also want to use util.manhattanDistance to calculate the distance
        between a particle and pacman's position.
        """

        noisyDistance = observation
        emissionModel = busters.getObservationDistribution(noisyDistance)
        pacmanPosition = gameState.getPacmanPosition()
        "*** YOUR CODE HERE ***"
        '''
        print "Noisy Distance: ", noisyDistance
        print "Emission Model: ", emissionModel
        print "pacman Position: ", pacmanPosition
        print "self.particles: ", self.particles
        '''
        allPossible = util.Counter()
        belief = self.getBeliefDistribution()
        #ghost has been captured
        if noisyDistance is None:
            self.particles = []
            for index in range(0, self.numParticles):
                self.particles.append(self.getJailPosition())
        else:
            #weighting and testing if the weights are 0
            for position in self.legalPositions:
                trueDistance = util.manhattanDistance(position, pacmanPosition)
                allPossible[position] = emissionModel[trueDistance] * belief[position]
            if allPossible.totalCount() == 0:
                self.initializeUniformly(gameState)
                return
            #resampling
            allPossible.normalize()
            self.particles = []
            for index in range(0, self.numParticles):
                newP = util.sample(allPossible)
                self.particles.append(newP)

    def observe(self, observation, gameState):

        noisyDistance = observation
        emissionModel = busters.getObservationDistribution(noisyDistance)
        pacmanPosition = gameState.getPacmanPosition()

        "*** YOUR CODE HERE ***"

	weights = util.Counter()
	i = 0	
	
	if noisyDistance == None:
		self.particle_positions = []
		while i != self.numParticles:
			self.particle_positions.append(self.getJailPosition())
			i += 1
	else:
		for p in self.particle_positions:
			trueDistance = util.manhattanDistance(p, pacmanPosition)
			#maybe more than one particle per position
			weights[p] += emissionModel[trueDistance]
	
		if weights.totalCount()	!= 0:
			self.particle_positions = []
			while i != self.numParticles:
				self.particle_positions.append(util.sample(weights))
				i += 1
		else:
			self.initializeUniformly(gameState)

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given
        its previous position (oldPos) as well as Pacman's current
        position.

        util.sample(Counter object) is a helper method to generate a sample from a
        belief distribution
        """
        "*** YOUR CODE HERE ***"
        # Updated: Bharadwaj Tanikella 2014

        temp = self.particles
        i = 0
        while i < len(temp):
            # newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))
            #print temp[i], Old Position
            newPostDict = self.getPositionDistribution(self.setGhostPosition(gameState,temp[i]))
            temp[i]=util.sample(newPostDict)
            i+=1
        self.particles= temp

  def observeState(self, gameState):
    """
    Resamples the set of particles using the likelihood of the noisy observations.

    As in elapseTime, to loop over the ghosts, use:

      for i in range(self.numGhosts):
        ...

    A correct implementation will handle two special cases:
      1) When a ghost is captured by Pacman, all particles should be updated so
         that the ghost appears in its prison cell, position (2 * i + 1, 1),
         where "i" is the 0-based index of the ghost.

         You can check if a ghost has been captured by Pacman by
         checking if it has a noisyDistance of 999 (a noisy distance
         of 999 will be returned if, and only if, the ghost is
         captured).

      2) When all particles receive 0 weight, they should be recreated from the
          prior distribution by calling initializeParticles.
    """

    pacmanPos = gameState.getPacmanPosition()
    noisyDistances = gameState.getNoisyGhostDistances()
    if len(noisyDistances) < self.numGhosts: return
    emissionModels = [busters.getObservationDistribution(dist) for dist in noisyDistances]

    jailed = [ noisy == 999 for noisy in noisyDistances ]

    partials = [ tuple() ] * self.numParticles

    for g in xrange(self.numGhosts):
      weighted = util.Counter()
      if jailed[g]:
        # handle the jailed ghost
        jailLocation = (2 * g + 1, 1)
        for i in xrange(self.numParticles):
          partials[i] += (jailLocation, )
        continue
      for oldAssign, counts in self.sampledCounts.iteritems():
        for assign, oldCount in counts.iteritems():
          if oldCount <= 0:
            continue
          trueDistance = util.manhattanDistance(pacmanPos, assign[g])
          delta = abs(trueDistance - noisyDistances[g])
          if emissionModels[g][trueDistance] > 0 and delta <= MAX_DIST_DELTA:
            # no need to normalize by constant
            pTrue = math.exp( -delta )
            weighted[assign[g]] = oldCount * emissionModels[g][trueDistance] * pTrue / self.proposals[oldAssign][assign]
      totalWeight = weighted.totalCount()
      if totalWeight != 0: weighted.normalize()
      for i in xrange(self.numParticles):
        if totalWeight == 0:
          #  handle the zero weights case
          partials[i] += (random.choice(self.legalPositions), )
        else:
          partials[i] += (util.sample(weighted), )

    self.particles = CounterFromIterable(partials)

  def elapseTime(self, gameState):
    "Update beliefs for a time step elapsing."
    "*** YOUR CODE HERE ***"
    temp = util.Counter()
    #print 'len of self.beliefs at the start of elapse time ',len(self.beliefs.keys())
    #print 'number of particles: ',self.numParticles
    for pos in self.beliefs.keys():

      #if self.beliefs[pos]==0: continue
            #print 'Ghost position ',pos
      #print 'Position distribution ', self.getPositionDistribution(gameState)
      #import time
      #print 'position ', pos
      state = self.setGhostPosition(gameState,pos)

      #if not pos in self.legalPositions:
        #print 'the position is not a legal position!! KERNEL PANIC'
        #time.sleep(20)

      #if self.getPositionDistribution
      #if state is None:
        #print 'state was none'
          
      #import time 
      #if len(self.getPositionDistribution(state)) is 0: 
        #print 'the class of state is ', state.__class__.__name__
        #print 'position distribution ', self.getPositionDistribution(state)
        #time.sleep(10000000)
      #print self.beliefs[pos]
      for i in range(self.beliefs[pos]):
        newSample = util.sample(self.getPositionDistribution(state))
        temp[newSample]+=1
    self.beliefs=temp

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given
        its previous position (oldPos) as well as Pacman's current
        position.

        util.sample(Counter object) is a helper method to generate a sample from a
        belief distribution
        """
        "*** YOUR CODE HERE ***"
            
        allPossible = util.Counter()
        newPosDist = util.Counter()
        currParticle = 0
        newParticleList = []
        for i in range(0, len(self.particleList)):
            newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, self.particleList[i]))
            newParticleList.append(util.sample(newPosDist))
        self.particleList = newParticleList

    def elapseTime(self, gameState):
        """
        Update beliefs for a time step elapsing.

        As in the elapseTime method of ExactInference, you should use:

          newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

        to obtain the distribution over new positions for the ghost, given its
        previous position (oldPos) as well as Pacman's current position.

        util.sample(Counter object) is a helper method to generate a sample from
        a belief distribution.
        """
        "*** YOUR CODE HERE ***"

        newParticleList = []

        allPossibleGhostDist = util.Counter()

        if self.particles[0] == self.getJailPosition():
            return

        '''
        for p in self.legalPositions:
            allPossibleGhostDist[p] = self.getPositionDistribution(self.setGhostPosition(gameState, p))
        '''

        for particle in self.particles:
            newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, particle))
            newParticleList.append(util.sample(newPosDist))

        self.particles = newParticleList

  def elapseTime(self, gameState):
    """
    Update beliefs for a time step elapsing.

    As in the elapseTime method of ExactInference, you should use:

      newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))

    to obtain the distribution over new positions for the ghost, given
    its previous position (oldPos) as well as Pacman's current
    position.
    """
    "*** YOUR CODE HERE ***"    
    temporaryPos = []
    temporaryWeight = []
    cnt = 0
    for oldPos in self.particles:
        oldWeight = self.particlesWeight[cnt]
        cnt += 1
        if not oldWeight > 0: continue
        newPosDist = self.getPositionDistribution(self.setGhostPosition(gameState, oldPos))
        newProb = 0
        while(newProb == 0):
            newPos = util.sample(newPosDist)
            newProb = newPosDist[newPos]
        temporaryPos.append(newPos)
        temporaryWeight.append(oldWeight)
    self.particles = temporaryPos
    self.particlesWeight = temporaryWeight

  def observe(self, observation, gameState):
    """
    Update beliefs based on the given distance observation. Make
    sure to handle the special case where all particles have weight
    0 after reweighting based on observation. If this happens,
    resample particles uniformly at random from the set of legal
    positions (self.legalPositions).

    A correct implementation will handle two special cases:
      1) When a ghost is captured by Pacman, all particles should be updated so
         that the ghost appears in its prison cell, self.getJailPosition()

         You can check if a ghost has been captured by Pacman by
         checking if it has a noisyDistance of None (a noisy distance
         of None will be returned if, and only if, the ghost is
         captured).
         
      2) When all particles receive 0 weight, they should be recreated from the
          prior distribution by calling initializeUniformly. Remember to
          change particles to jail if called for.
    """
    noisyDistance = observation
    emissionModel = busters.getObservationDistribution(noisyDistance)
    pacmanPosition = gameState.getPacmanPosition()

    # check if all weights are zero
    def zeroWeights(weights):
      return all(w == 0 for w in weights.values())

    
    prevBelief = self.getBeliefDistribution()
    allPossible = util.Counter()
    nextParticles = []

    # ghost captured
    if noisyDistance is None:
      jailPosition = self.getJailPosition()
      
      # put ghost to jail
      for i in range(self.numParticles):
        nextParticles.append(jailPosition)

      self.particles = nextParticles

    else:
      # update beliefs
      for pos in self.legalPositions:
        trueDistance = util.manhattanDistance(pos, pacmanPosition)
        allPossible[pos] += emissionModel[trueDistance] * prevBelief[pos]
      
      # weights all zero
      if zeroWeights(allPossible):
        self.initializeUniformly(gameState)

      else:
        # resample particles
        for i in range(self.numParticles):
          nextParticles.append(util.sample(allPossible))

        self.particles = nextParticles

    def observeState(self, gameState):
        """
        Resamples the set of particles using the likelihood of the noisy
        observations.

        To loop over the ghosts, use:

          for i in range(self.numGhosts):
            ...

        A correct implementation will handle two special cases:
          1) When a ghost is captured by Pacman, all particles should be updated
             so that the ghost appears in its prison cell, position
             self.getJailPosition(i) where `i` is the index of the ghost.

             As before, you can check if a ghost has been captured by Pacman by
             checking if it has a noisyDistance of None.

          2) When all particles receive 0 weight, they should be recreated from
             the prior distribution by calling initializeParticles. After all
             particles are generated randomly, any ghosts that are eaten (have
             noisyDistance of None) must be changed to the jail Position. This
             will involve changing each particle if a ghost has been eaten.

        self.getParticleWithGhostInJail is a helper method to edit a specific
        particle. Since we store particles as tuples, they must be converted to
        a list, edited, and then converted back to a tuple. This is a common
        operation when placing a ghost in jail.
        """
        pacmanPosition = gameState.getPacmanPosition()
        noisyDistances = gameState.getNoisyGhostDistances()
        if len(noisyDistances) < self.numGhosts:
            return
        emissionModels = [busters.getObservationDistribution(dist) for dist in noisyDistances]

        "*** YOUR CODE HERE ***"
        #first special case
        for i in xrange(self.numGhosts):
        	if noisyDistances[i]==None:
        		for x, y in enumerate(self.particles):
					self.particles[x] = self.getParticleWithGhostInJail(y, i)
        #create a weighted particle distribution
        weightedParticleDistri = util.Counter()
        for particle in self.particles:
        	product = 1
        	for i in xrange(self.numGhosts):
        		if noisyDistances[i]!=None:
        			trueDistance = util.manhattanDistance(particle[i], pacmanPosition)
        			product *= emissionModels[i][trueDistance]
        	weightedParticleDistri[particle] += product
        # second special case
        if weightedParticleDistri.totalCount()==0:
            self.initializeParticles()
            #change all particles with all the eaten ghosts' positions changed to their respective jail positions
            for i in xrange(self.numGhosts):
	        	if noisyDistances[i]==None:
	        		for x, y in enumerate(self.particles):
						self.particles[x] = self.getParticleWithGhostInJail(y, i)
        else: # resampling
            self.particles = [util.sample(weightedParticleDistri) for particle in self.particles]

 def elapseTime(self, gameState):
   """
   Samples each particle's next state based on its current state and the gameState.
   
   You will need to use two helper methods provided below:
     1) setGhostPositions(gameState, ghostPositions)
         This method alters the gameState by placing the ghosts in the supplied positions.
     
     2) getPositionDistributionForGhost(gameState, ghostIndex, agent)
         This method uses the supplied ghost agent to determine what positions 
         a ghost (ghostIndex) controlled by a particular agent (ghostAgent) 
         will move to in the supplied gameState.  All ghosts
         must first be placed in the gameState using setGhostPositions above.
         Remember: ghosts start at index 1 (Pacman is agent 0).  
         
         The ghost agent you are meant to supply is self.enemyAgents[ghostIndex-1],
         but in this project all ghost agents are always the same.
   """
   newParticles = []
   for oldParticle in self.particles:
     newParticle = list(oldParticle) # A list of ghost positions
     for enemyIndex in range(len(self.enemyIndices)):
       tmpState = setEnemyPositions(gameState, newParticle, self.enemyIndices)    
       updatedParticle = util.sample(getPositionDistributionForEnemy(tmpState, self.enemyIndices[enemyIndex], self.enemyIndices[enemyIndex]))
       newParticle[enemyIndex] = updatedParticle
     newParticles.append(tuple(newParticle))
   self.particles = newParticles