Merge pull request #1016 from souravsingh/new-strategy

Add EugineNier strategy from LessWrong

Author: marcharper

axelrod/strategies/_strategies.py

@@ -76,7 +76,7 @@
     TitForTat, TitFor2Tats, TwoTitsForTat, Bully, SneakyTitForTat,
     SuspiciousTitForTat, AntiTitForTat, HardTitForTat, HardTitFor2Tats,
     OmegaTFT, Gradual, ContriteTitForTat, SlowTitForTwoTats, AdaptiveTitForTat,
-    SpitefulTitForTat, SlowTitForTwoTats2, Alexei)
+    SpitefulTitForTat, SlowTitForTwoTats2, Alexei, EugineNier)
 from .verybad import VeryBad
 from .worse_and_worse import (WorseAndWorse, KnowledgeableWorseAndWorse,
                               WorseAndWorse2, WorseAndWorse3)
@@ -126,6 +126,7 @@
     DoubleResurrection,
     EasyGo,
     Eatherley,
+    EugineNier,
     EventualCycleHunter,
     EvolvedANN,
     EvolvedANN5,

axelrod/strategies/titfortat.py

@@ -642,10 +642,10 @@ def strategy(self, opponent: Player) -> Action:
 class Alexei(Player):
     """
     Plays similar to Tit-for-Tat, but always defect on last turn.
-    
+
     Names:
 
-    - Alexei's Strategy: [LessWrong2011]_    
+    - Alexei: [LessWrong2011]_
     """
 
     name = 'Alexei'
@@ -665,3 +665,43 @@ def strategy(self, opponent: Player) -> Action:
         if opponent.history[-1] == D:
             return D
         return C
+
+@FinalTransformer((D,), name_prefix=None)
+class EugineNier(Player):
+    """
+    Plays similar to Tit-for-Tat, but with two conditions:
+    1) Always Defect on Last Move
+    2) If other player defects five times, switch to all defects.
+
+    Names:
+
+    - Eugine Nier: [LessWrong2011]_
+    """
+
+    name = 'EugineNier'
+    classifier = {
+        'memory_depth': float('inf'),
+        'stochastic': False,
+        'makes_use_of': {'length'},
+        'long_run_time': False,
+        'inspects_source': False,
+        'manipulates_source': False,
+        'manipulates_state': False
+    }
+
+    def __init__(self):
+        super().__init__()
+        self.is_defector = False
+
+    def strategy(self, opponent: Player) -> Action:
+        if not self.history:
+            return C
+        if not (self.is_defector) and opponent.defections >= 5:
+            self.is_defector = True
+        if self.is_defector:
+            return D
+        return opponent.history[-1]
+
+    def reset(self):
+        super().reset()
+        self.is_defector = False

axelrod/tests/strategies/test_titfortat.py

@@ -593,10 +593,56 @@ def test_strategy(self):
         actions = [(C, C), (C, D), (D, C), (C, D), (D, C), (C, D)]
         self.versus_test(axelrod.Alternator(), expected_actions=actions,
                          match_attributes={"length": -1})
-        
+
         actions = [(C, C), (C, D), (D, C), (C, D), (D, C), (D, D)]
         self.versus_test(axelrod.Alternator(), expected_actions=actions)
 
         opponent = axelrod.MockPlayer(actions=[C, C, D, D, C, D])
         actions = [(C, C), (C, C), (C, D), (D, D), (D, C), (D, D)]
         self.versus_test(opponent, expected_actions=actions)
+
+class TestEugineNier(TestPlayer):
+    """
+    Tests for the Eugine Nier strategy
+    """
+
+    name = "EugineNier: ('D',)"
+    player = axelrod.EugineNier
+    expected_classifier = {
+        'memory_depth': float('inf'),
+        'stochastic': False,
+        'makes_use_of': {'length'},
+        'inspects_source': False,
+        'manipulates_source': False,
+        'manipulates_state': False
+    }
+
+    def test_strategy(self):
+        self.first_play_test(C)
+        self.second_play_test(rCC=C, rCD=D, rDC=C, rDD=D)
+
+        actions = [(C, C), (C, C), (C, C), (D, C)]
+        self.versus_test(axelrod.Cooperator(), expected_actions=actions,
+                         attrs={"is_defector": False})
+
+        actions = [(C, C), (C, C), (C, C), (C, C)]
+        self.versus_test(axelrod.Cooperator(), expected_actions=actions,
+                         attrs={"is_defector": False},
+                         match_attributes={"length": -1})
+
+
+        # Plays TfT and defects in last round
+        actions = [(C, C), (C, D), (D, C), (C, D), (D, C), (D, D)]
+        self.versus_test(axelrod.Alternator(), expected_actions=actions,
+                         attrs={"is_defector": False})
+
+        actions = [(C, C), (C, D), (D, C), (C, D), (D, C), (C, D)]
+        self.versus_test(axelrod.Alternator(), expected_actions=actions,
+                         attrs={"is_defector": False},
+                         match_attributes={"length": -1})
+
+        # Becomes defector after 5 defections
+        opponent = axelrod.MockPlayer(actions=[D, C, D, D, D, D, C, C])
+        actions = [(C, D), (D, C), (C, D), (D, D),
+                   (D, D), (D, D), (D, C), (D, C)]
+        self.versus_test(opponent, expected_actions=actions)

docs/tutorials/advanced/classification_of_strategies.rst

@@ -80,7 +80,7 @@ length of each match of the tournament::
     ... }
     >>> strategies = axl.filtered_strategies(filterset)
     >>> len(strategies)
-    27
+    28
 
 Note that in the filterset dictionary, the value for the 'makes_use_of' key
 must be a list. Here is how we might identify the number of strategies that use