SteinAndRapoport Strategy

Author: MariosZoulias

axelrod/strategies/_strategies.py

@@ -72,6 +72,7 @@
 from .selfsteem import SelfSteem
 from .shortmem import ShortMem
 from .stalker import Stalker
+from .axelrod_first import SteinAndRapoport
 from .titfortat import (
     TitForTat, TitFor2Tats, TwoTitsForTat, Bully, SneakyTitForTat,
     SuspiciousTitForTat, AntiTitForTat, HardTitForTat, HardTitFor2Tats,
@@ -232,6 +233,7 @@
     SolutionB5,
     SpitefulTitForTat,
     Stalker,
+    SteinAndRapoport,
     StochasticCooperator,
     StochasticWSLS,
     SuspiciousTitForTat,

axelrod/strategies/axelrod_first.py

@@ -8,6 +8,8 @@
 from axelrod.player import Player
 from axelrod.random_ import random_choice
 from.memoryone import MemoryOnePlayer
+from axelrod.strategy_transformers import FinalTransformer
+from scipy.stats import chisquare
 
 from typing import List, Dict, Tuple
 
@@ -487,3 +489,69 @@ class UnnamedStrategy(Player):
     def strategy(opponent: Player) -> Action:
         r = random.uniform(3, 7) / 10
         return random_choice(r)
+
+@FinalTransformer((D, D), name_prefix=None)
+class SteinAndRapoport(Player):
+    """
+        A player who plays according to statistic methods.
+        Begins by playing C for the first four (4) rounds , then it plays
+        tit for tat and at the last 2 round it Defects. Every 15 turns it
+        run a chi-squared test to check whether the opponent behaves randomly
+        or not . In case the opponent behaves randomly then Stein_and_Rapoport
+        Defects untill the next 15 round (where we check again), otherwise he
+        still plays TitForTat.
+    """
+
+    name = 'Stein and Rapoport'
+    classifier = {
+        'memory_depth': 15,
+        'stochastic': False,
+        'makes_use_of': set(),
+        'long_run_time': False,
+        'inspects_source': False,
+        'manipulates_source': False,
+        'manipulates_state': False
+    }
+
+    def __init__(self, alpha: float=0.05) -> None:
+        """
+        Parameters
+        ----------
+        alpha, float
+            The significant level of pvalue from chi-squared test
+            0.05 by default according to literature
+        """
+        super().__init__()
+        self.alpha = alpha
+        if (self.alpha > 1) or (self.alpha < 0):
+            self.alpha = 0.05
+
+    def strategy(self , opponent: Player , chi_tests = [0]) -> Action:
+        # chi-tests == 0 then we play TitForTat
+        round_number = len(self.history) + 1
+
+        # First 4 moves
+        if round_number < 5 :
+            return C
+
+        # For first 15 rounds tit for tat as we dont know opponents strategy
+        if round_number < 16 :
+            if opponent.history[-1] == 'D' :
+                return D
+            else :
+                return C
+
+        if len(self.history) % 15 == 0 :
+            if chisquare([opponent.cooperations, opponent.defections]).pvalue >= self.alpha :
+                chi_tests.append(1)
+            else :
+                chi_tests.append(0)
+
+        if chi_tests[-1] == 1 :
+            # Defect if opponent plays randomly
+            return D
+        else : # TitForTatat if opponent plays not randomly
+            if opponent.history[-1] == 'D' :
+                return D
+            else :
+                return C

axelrod/tests/strategies/test_axelrod_first.py

@@ -387,3 +387,41 @@ def test_strategy(self):
         actions = [(C, C), (C, C), (D, C), (C, C), (C, C), (D, C)]
         self.versus_test(axelrod.Cooperator(), expected_actions=actions,
                          seed=10)
+
+
+class SteinAndRapoport(TestPlayer):
+
+    name = "SteinAndRapoport"
+    player = axelrod.SteinAndRapoport
+    expected_classifier = {
+        'memory_depth': 15,
+        'long_run_time': False,
+        'stochastic': False,
+        'makes_use_of': set(),
+        'inspects_source': False,
+        'manipulates_source': False,
+        'manipulates_state': False
+    }
+
+    def test_strategy(self):
+        self.first_play_test(C)
+
+        # Our Player (SteinAndRapoport) vs Cooperator
+        # After 15th round (pvalue < alpha) still plays titfortat
+        opponent = axelrod.Cooperator()
+        actions = [(C, C)] * 17 + [(D, C)] * 2
+        self.versus_test(opponent, expected_actions=actions)
+
+        # Our Player (SteinAndRapoport) vs Defector
+        # After 15th round (pvalue < alpha) still plays titfortat
+        opponent = axelrod.Cooperator()
+        actions = [(C, D)] * 4 + [(D, D)] * 15
+        self.versus_test(opponent, expected_actions=actions)
+
+        # Our Player (SteinAndRapoport) vs Alternator
+        # After 15th round (pvalue > alpha) starts defect
+        opponent = axelrod.Alternator()
+        actions = [(C, C), (C, D), (C, C), (C, D), (D, C), (C, D), (D, C),
+                  (C, D), (D, C), (C, D), (D, C), (C, D),(D, C), (C, D),
+                  (D, C), (D, D), (D, C), (D, D), (D, C)]
+        self.versus_test(opponent, expected_actions=actions)