Meta Winner Ensemble strategy

axelrod/strategies/__init__.py

@@ -10,13 +10,14 @@
     MetaPlayer, MetaMajority, MetaMinority, MetaWinner, MetaHunter,
     MetaMajorityMemoryOne, MetaWinnerMemoryOne, MetaMajorityFiniteMemory,
     MetaWinnerFiniteMemory, MetaMajorityLongMemory, MetaWinnerLongMemory,
-    MetaMixer
+    MetaMixer, MetaWinnerEnsemble
     )
 
 all_strategies.extend([MetaHunter, MetaMajority, MetaMinority, MetaWinner,
                        MetaMajorityMemoryOne, MetaWinnerMemoryOne,
                        MetaMajorityFiniteMemory, MetaWinnerFiniteMemory,
-                       MetaMajorityLongMemory, MetaWinnerLongMemory, MetaMixer])
+                       MetaMajorityLongMemory, MetaWinnerLongMemory, MetaMixer,
+                       MetaWinnerEnsemble])
 
 
 # Distinguished strategy collections in addition to

axelrod/strategies/meta.py

@@ -1,4 +1,4 @@
-from axelrod import Actions, Player, obey_axelrod
+from axelrod import Actions, Player, obey_axelrod, random_choice
 from ._strategies import all_strategies
 from .hunter import (
     DefectorHunter, AlternatorHunter, RandomHunter, MathConstantHunter,
@@ -165,6 +165,32 @@ def meta_strategy(self, results, opponent):
 
         return bestresult
 
+class MetaWinnerEnsemble(MetaWinner):
+    """A variant of MetaWinner that chooses one of the top scoring strategies at random against each opponent."""
+
+    name = "Meta Winner Ensemble"
+
+    def meta_strategy(self, results, opponent):
+        # Sort by score
+        scores = [(pl.score, i) for (i, pl) in enumerate(self.team)]
+        # Choose one of the best scorers at random
+        scores.sort(reverse=True)
+        prop = max(1, int(len(scores) * 0.08))
+        index = choice([i for (s, i) in scores[:prop]])
+
+        # Update each player's proposed history with his proposed result, but
+        # always after the new result has been settled based on scores
+        # accumulated until now.
+        for r, t in zip(results, self.team):
+            t.proposed_history.append(r)
+
+        if opponent.defections == 0:
+            # Don't poke the bear
+            return C
+
+        # return result
+        return results[index]
+
 
 class MetaHunter(MetaPlayer):
     """A player who uses a selection of hunters."""

axelrod/tests/unit/test_meta.py

@@ -185,6 +185,27 @@ def test_strategy(self):
         self.assertEqual(player.history[-1], D)
 
 
+class TestMetaWinnerEnsemble(TestMetaPlayer):
+    name = "Meta Winner Ensemble"
+    player = axelrod.MetaWinnerEnsemble
+    expected_classifier = {
+        'memory_depth': float('inf'),  # Long memory
+        'stochastic': True,
+        'makes_use_of': set(['game']),
+        'long_run_time': True,
+        'inspects_source': False,
+        'manipulates_source': False,
+        'manipulates_state': False
+    }
+
+    expected_class_classifier = copy.copy(expected_classifier)
+    expected_class_classifier['stochastic'] = False
+    expected_class_classifier['makes_use_of'] = set([])
+
+    def test_strategy(self):
+        self.first_play_test(C)
+
+
 class TestMetaHunter(TestMetaPlayer):
 
     name = "Meta Hunter"

docs/tutorials/advanced/classification_of_strategies.rst

@@ -101,7 +101,7 @@ Some strategies have been classified as having a particularly long run time::
     ... }
     >>> strategies = axl.filtered_strategies(filterset)
     >>> len(strategies)
-    10
+    11
 
 Strategies that :code:`manipulate_source`, :code:`manipulate_state`
 and/or :code:`inspect_source` return :code:`False` for the :code:`obey_axelrod`