zaiSearch3

Authorzdg
Submission date2011-09-05 16:27:56.757782
Rating5843
Matches played2667
Win rate58.01

Use rpsrunner.py to play unranked matches on your computer.

Source code:

# searching for a past pattern and using it to predict the opponent's next move
# seems like only matching opponent's hands is better than trying to match opponents and own hands
# also only consider patterns after which the opponent wins or ties, since the opponent is more likely to play those hands

# minor tweak of weights

import math
import random

# the hand that beats this hand
beats = {'R':'P', 'P':'S', 'S':'R'}

# returns a weighted random choice of R, P or S
# default with no arguments is uniformly random
def rand_hand(probs=None,sum=None):
   if probs is None:
      return random.choice(['R', 'P', 'S'])
   else:
      if sum is None:
         sum = probs['R'] + probs['P'] + probs['S']
      if sum < 0.5:
         return random.choice(['R', 'P', 'S'])
      r = random.uniform(0, sum)
      if r < probs['R']:
         return 'R'
      elif r < probs['R'] + probs['P']:
         return 'P'
      else:
         return 'S'

def win(mine, other):
   return mine == beats[other]

# finds the length of the match from searchIndex and matchIndex leftward
def searchPatternLengthBackwards(lst, searchIndex, matchIndex, indexLimit, lengthLimit):
   length = 0
   while searchIndex >= indexLimit and matchIndex >= indexLimit and \
      length < lengthLimit and lst[searchIndex] == lst[matchIndex]:
      searchIndex -= 1
      matchIndex -= 1
      length += 1
   return length

# calculates the weight of a pattern match based on length and distance
# the distance is from the index where the match is found to the current playing index
def weighPattern(length, lengthLimit, distance, distanceLimit):
   if length > 0:
      temp = length * length
      temp2 = temp * temp
      lengthWeight = temp
      distanceWeight = ((distanceLimit - distance) / float(distanceLimit)) + 1
      return lengthWeight * distanceWeight
   else:
      return 0

# calculates the weights of the opponent's next move
def calculateWeights(lst, index, distanceLimit, lengthLimit):
   indexLimit = index - distanceLimit
   weights = {'R':0.0, 'P':0.0, 'S':0.0}
   for i in xrange(index - 1, indexLimit - 1, -1):
      length = searchPatternLengthBackwards(lst, i, index, indexLimit, lengthLimit)
      distance = index - i
      # count it only if after that pattern was a tie or a loss
      if not win(my_hands[i+1], lst[i+1]):
         weight = weighPattern(length, lengthLimit, distance, distanceLimit)
         if weight > 0:
            weights[lst[i+1]] += weight
   return weights

# uses the calculated weights to make a prediction about the opponent's next hand
def predict(lst, index, distanceLimit, lengthLimit,):
   weights = calculateWeights(lst, index, distanceLimit, lengthLimit)
   return rand_hand(weights)

# start of main code
if input == '':
   hands_played = []
   my_hands = []
   hands = 1
   
   output = rand_hand()
   lastHand = output
else:
   hands_played.append(input)
   my_hands.append(lastHand)
   
   distanceLimit = min(hands - 1, 1000)
   lengthLimit = min(hands - 1, 10)
   
   prediction = predict(hands_played, hands - 1, lengthLimit, distanceLimit)
   output = beats[prediction]
   
   lastHand = output
   hands += 1