Rename and fix Tullock.

I believe the logic was slightly faulty for Tullock: the first 11 moves
was correct however once past there we should only be considering the 10
previous moves.

Author: drvinceknight

axelrod/strategies/_strategies.py

@@ -16,7 +16,7 @@
     FirstByShubik,
     SteinAndRapoport,
     TidemanAndChieruzzi,
-    Tullock,
+    FirstByTullock,
     UnnamedStrategy,
 )
 from .axelrod_second import (
@@ -430,7 +430,7 @@
     TrickyCooperator,
     TrickyDefector,
     TrickyLevelPunisher,
-    Tullock,
+    FirstByTullock,
     TwoTitsForTat,
     UsuallyCooperates,
     UsuallyDefects,

axelrod/strategies/axelrod_first.py

@@ -593,12 +593,23 @@ def strategy(self, opponent: Player) -> Action:
         return C
 
 
-class Tullock(Player):
+class FirstByTullock(Player):
     """
     Submitted to Axelrod's first tournament by Gordon Tullock.
 
+    The description written in [Axelrod1980]_ is:
+
+    > "This rule cooperates on the first eleven moves. It then cooperates 10%
+    > less than the other player has cooperated on the preceding ten moves. This
+    > rule is based on an idea developed in Overcast and Tullock (1971). Professor
+    > Tullock was invited to specify how the idea could be implemented, and he did
+    > so out of scientific interest rather than an expectation that it would be a
+    > likely winner."
+
+    This is interpreted as:
+
     Cooperates for the first 11 rounds then randomly cooperates 10% less often
-    than the opponent has in previous rounds.
+    than the opponent has in the previous 10 rounds.
 
     This strategy came 13th in Axelrod's original tournament.
 
@@ -607,9 +618,9 @@ class Tullock(Player):
     - Tullock: [Axelrod1980]_
     """
 
-    name = "Tullock"
+    name = "First tournament by Tullock"
     classifier = {
-        "memory_depth": 11,  # long memory, modified by init
+        "memory_depth": 11,
         "stochastic": True,
         "makes_use_of": set(),
         "long_run_time": False,
@@ -622,17 +633,17 @@ def __init__(self, rounds_to_cooperate: int = 11) -> None:
         """
         Parameters
         ----------
-        rounds_to_cooperate: int, 10
+        rounds_to_cooperate: int
            The number of rounds to cooperate initially
         """
         super().__init__()
         self._rounds_to_cooperate = rounds_to_cooperate
         self.memory_depth = rounds_to_cooperate
 
     def strategy(self, opponent: Player) -> Action:
-        rounds = self._rounds_to_cooperate
-        if len(self.history) < rounds:
+        if len(self.history) < self._rounds_to_cooperate:
             return C
+        rounds = self._rounds_to_cooperate - 1
         cooperate_count = opponent.history[-rounds:].count(C)
         prop_cooperate = cooperate_count / rounds
         prob_cooperate = max(0, prop_cooperate - 0.10)

axelrod/tests/strategies/test_axelrod_first.py

@@ -404,10 +404,10 @@ def test_strategy(self):
         self.versus_test(opponent, expected_actions=actions)
 
 
-class TestTullock(TestPlayer):
+class TestFirstByTullock(TestPlayer):
 
-    name = "Tullock: 11"
-    player = axelrod.Tullock
+    name = "First tournament by Tullock: 11"
+    player = axelrod.FirstByTullock
     expected_classifier = {
         "memory_depth": 11,
         "stochastic": True,

docs/reference/overview_of_strategies.rst

@@ -28,7 +28,7 @@ An indication is given as to whether or not this strategy is implemented in the
   "Downing", "Leslie Downing", ":class:`RevisedDowning <axelrod.strategies.axelrod_first.RevisedDowning>`"
   "Feld", "Scott Feld", ":class:`Feld <axelrod.strategies.axelrod_first.FirstByFeld>`"
   "Joss", "Johann Joss", ":class:`Joss <axelrod.strategies.axelrod_first.FirstByJoss>`"
-  "Tullock",  "Gordon Tullock", ":class:`Tullock <axelrod.strategies.axelrod_first.Tullock>`"
+  "Tullock",  "Gordon Tullock", ":class:`Tullock <axelrod.strategies.axelrod_first.FirstByTullock>`"
   "Unnamed Strategy", "Unknown", ":class:`UnnamedStrategy <axelrod.strategies.axelrod_first.UnnamedStrategy>`"
   "Random", "Unknownd", ":class:`Random <axelrod.strategies.rand.Random>`"