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HW1/MDP.py

+class MDP(object):
+	def __init__(self):
+
+		# Possible states are e;ements of [0,1,...,5] x [0,1,...,5]
+		# and two additional states to indicate GOALS and OUT (Wayward kicks)
+		self.S = [(x,y) for x in range(5) for y in range(5)]
+		self.S.append("GOAL")
+		self.S.append("OUT")
+
+		# Agent possible actions
+		self.A = ["DRIBBLE_UP","DRIBBLE_DOWN","DRIBBLE_LEFT","DRIBBLE_RIGHT","SHOOT"]
+
+		# Opposition locations
+		self.oppositions = [(2,2), (4,2)]
+
+		# Probability of scoring from locations in the pitch
+		# each list inside goalProbs represents probability of scoring goal
+		# for grids in a column, starting from the leftmost column
+		self.goalProbs = [[0.00,0.00,0.0,0.00,0.00],[0.0, 0.0,0.0,0.0,0.0],[0.0,0.0,0.0,0.0,0.0],[0.0,0.3,0.5,0.3,0.0],[0.0,0.8,0.9,0.8,0.0]]
+
+	def getRewards(self, initState, Action, nextState):
+		""" Return R(s,a,s') for the MDP 
+
+		Keyword Arguments:
+		initState -- The current state s.
+		action -- The chosen action in state s, a.
+		nextState -- The next state s'
+		"""
+		if nextState == "GOAL": # Rewards if agents managed to score a goal
+			if initState != "GOAL":
+				return 1
+			else:
+				return 0
+
+		elif nextState == "OUT":
+			if initState != "OUT":
+				return -1
+			else:
+				return 0
+		elif nextState in self.oppositions : # Rewards if agent bumped into opposition placed in (2,2) and (4,2)
+			return -0.5
+		else :
+			return 0
+
+	def probNextStates(self, initState, action):
+		""" Return the next state probability for the MDP as a dictionary.
+
+		Keyword Arguments:
+		initState -- The current state s.
+		action -- The chosen action in state s, a.
+
+		"""
+		nextStateProbs = {}
+		if initState != "GOAL" and initState!="OUT":
+			if action != "SHOOT":
+
+				possibleDestinations = [(initState[0], max(0,initState[1]-1)),(initState[0], min(4,initState[1]+1)),
+										(max(0,initState[0]-1), initState[1]), (min(4,initState[0]+1), initState[1])]
+
+				intendedDestination = None
+				if action == "DRIBBLE_UP":
+					intendedDestination = (initState[0], max(0,initState[1]-1))
+				elif action == "DRIBBLE_DOWN" :
+					intendedDestination = (initState[0], min(4,initState[1]+1))
+				elif action == "DRIBBLE_LEFT" :
+					intendedDestination = (max(0,initState[0]-1), initState[1])
+				else:
+					intendedDestination = (min(4,initState[0]+1), initState[1])
+			
+				nextStateProbs[intendedDestination] = 0.8
+				for intendedDestination in possibleDestinations :
+					if not intendedDestination in nextStateProbs.keys():
+						nextStateProbs[intendedDestination] = 0.0
+					nextStateProbs[intendedDestination] += 0.05
+
+			else :
+
+				nextStateProbs["GOAL"] = self.goalProbs[initState[0]][initState[1]]
+				nextStateProbs["OUT"] = 1.0-nextStateProbs["GOAL"]
+
+		elif initState=="GOAL":
+			nextStateProbs["GOAL"] = 1.0
+		else:
+			nextStateProbs["OUT"] = 1.0
+
+		return nextStateProbs
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