Merge pull request #671 from Axelrod-Python/670

Simplify (and correct) mean payoff diff scores

Author: meatballs

axelrod/result_set.py

@@ -464,28 +464,8 @@ def build_payoff_diffs_means(self):
             Where pij is the mean difference of the
             scores per turn between player i and j in repetition m.
         """
-        plist = list(range(self.nplayers))
-        payoff_diffs_means = [[0 for opponent in plist] for player in plist]
-
-        for player in plist:
-            for opponent in plist:
-                diffs = []
-                for index_pair, repetitions in self.interactions.items():
-                    if (player, opponent) == index_pair:
-                        for interaction in repetitions:
-                            scores = iu.compute_final_score_per_turn(interaction,
-                                                                     self.game)
-                            diffs.append(scores[0] - scores[1])
-                    elif (opponent, player) == index_pair:
-                        for interaction in repetitions:
-                            scores = iu.compute_final_score_per_turn(interaction,
-                                                                    self.game)
-                            diffs.append(scores[1] - scores[0])
-                if diffs:
-                    payoff_diffs_means[player][opponent] = mean(diffs)
-                else:
-                    payoff_diffs_means[player][opponent] = 0
-
+        payoff_diffs_means = [[mean(diff) for diff in player]
+                              for player in self.score_diffs]
         return payoff_diffs_means
 
     @update_progress_bar

axelrod/tests/unit/test_resultset.py

@@ -364,6 +364,14 @@ def test_eigenmoses_rating(self):
         for j, rate in enumerate(rs.eigenmoses_rating):
             self.assertAlmostEqual(rate, self.expected_eigenmoses_rating[j])
 
+    def test_self_interaction_for_random_strategies(self):
+        # Based on https://github.com/Axelrod-Python/Axelrod/issues/670
+        axelrod.seed(0)
+        players = [s() for s in axelrod.demo_strategies]
+        tournament = axelrod.Tournament(players, repetitions=2, turns=5)
+        results = tournament.play()
+        self.assertEqual(results.payoff_diffs_means[-1][-1], 1.0)
+
 
 class TestResultSetFromFile(unittest.TestCase):
     tmp_file = tempfile.NamedTemporaryFile(mode='w', delete=False)