Refactor function to check that graph is connected

Author: drvinceknight

axelrod/match_generator.py

@@ -169,6 +169,31 @@ def estimated_size(self):
         return size
 
 
+def test_graph_is_connected(edges, players):
+    """
+    Test if a set of edges defines a complete graph on a set of players.
+
+    This is used by the spatial tournaments and will raise a ValueError if the
+    graph would have some players not playing anyone.
+
+    Parameters:
+    -----------
+
+        edges : a list of 2 tuples
+        players : a list of player names
+    """
+    # Check if all players are connected.
+    player_indices = set(range(len(players)))
+    node_indices = set()
+    for edge in edges:
+        for node in edge:
+            node_indices.add(node)
+
+    if player_indices != node_indices:
+        raise ValueError("The graph edges do not include all players.")
+
+
+
 class SpatialMatches(RoundRobinMatches):
     """
     A class that generates spatially-structured matches.
@@ -192,16 +217,7 @@ class SpatialMatches(RoundRobinMatches):
 
     def __init__(self, players, turns, game, repetitions, edges):
 
-        # Check if all players are connected.
-        player_indices = set(range(len(players)))
-        node_indices = set()
-        for edge in edges:
-            for node in edge:
-                node_indices.add(node)
-
-        if player_indices != node_indices:
-            raise ValueError("The graph edges do not include all players.")
-
+        test_graph_is_connected(edges, players)
         self.edges = edges
         super(SpatialMatches, self).__init__(players, turns, game, repetitions)
 
@@ -238,16 +254,7 @@ class ProbEndSpatialMatches(SpatialMatches, ProbEndRoundRobinMatches):
 
     def __init__(self, players, prob_end, game, repetitions, noise, edges):
 
-        # Check if all players are connected.
-        player_indices = set(range(len(players)))
-        node_indices = set()
-        for edge in edges:
-            for node in edge:
-                node_indices.add(node)
-
-        if player_indices != node_indices:
-            raise ValueError("The graph edges do not include all players.")
-
+        test_graph_is_connected(edges, players)
         self.edges = edges
         ProbEndRoundRobinMatches.__init__(self, players, prob_end,
                                           game, repetitions, noise)

axelrod/tests/unit/test_match_generator.py

@@ -5,6 +5,7 @@
 from hypothesis.strategies import floats, integers
 
 import axelrod
+from axelrod.match_generator import test_graph_is_connected
 
 
 test_strategies = [
@@ -319,3 +320,15 @@ def test_noise(self, noise, prob_end):
                         for (index_pair, match_params, repetitions) in chunks]
         for value in noise_values:
             self.assertEqual(noise, value)
+
+
+class TestUtilityFunctions(unittest.TestCase):
+    def test_connected_graph(self):
+        edges = [(0, 0), (0, 1), (1, 1)]
+        players = ["Cooperator", "Defector"]
+        self.assertEqual(test_graph_is_connected(edges, players), None)
+
+    def test_unconnected_graph(self):
+        edges = [(0, 0), (0, 1), (1, 1)]
+        players = ["Cooperator", "Defector", "Alternator"]
+        self.assertRaises(ValueError, test_graph_is_connected, edges, players)