651 - Tests for random seeding and a random seeding function

axelrod/__init__.py

@@ -2,7 +2,7 @@
 
 # The order of imports matters!
 from .actions import Actions, flip_action
-from .random_ import random_choice
+from .random_ import random_choice, set_seed
 from .plot import Plot
 from .game import DefaultGame, Game
 from .player import init_args, is_basic, obey_axelrod, update_history, Player

axelrod/random_.py

@@ -1,4 +1,5 @@
 import random
+import numpy
 from axelrod import Actions
 
 
@@ -21,3 +22,9 @@ def randrange(a, b):
     c = b - a
     r = c * random.random()
     return a + int(r)
+
+
+def set_seed(seed):
+    """Sets a seed"""
+    random.seed(seed)
+    numpy.random.seed(seed)

axelrod/tests/integration/test_matches.py

@@ -11,6 +11,10 @@
 deterministic_strategies = [s for s in axelrod.ordinary_strategies
                             if not s().classifier['stochastic']]  # Well behaved strategies
 
+stochastic_strategies = [s for s in axelrod.ordinary_strategies
+                         if s().classifier['stochastic']]
+
+
 class TestMatchOutcomes(unittest.TestCase):
 
     @given(strategies=strategy_lists(strategies=deterministic_strategies,
@@ -23,3 +27,19 @@ def test_outcome_repeats(self, strategies, turns):
         matches = [axelrod.Match(players, turns) for _ in range(3)]
         self.assertEqual(matches[0].play(), matches[1].play())
         self.assertEqual(matches[1].play(), matches[2].play())
+
+    @given(strategies=strategy_lists(strategies=stochastic_strategies,
+                                     min_size=2, max_size=2),
+           turns=integers(min_value=1, max_value=20),
+           seed=integers(min_value=0, max_value=4294967295))
+    def test_outcome_repeats_stochastic(self, strategies, turns, seed):
+        """a test to check that if a seed is set stochastic strategies give the
+        same result"""
+        results = []
+        for _ in range(3):
+            axelrod.set_seed(seed)
+            players = [s() for s in strategies]
+            results.append(axelrod.Match(players, turns).play())
+
+        self.assertEqual(results[0], results[1])
+        self.assertEqual(results[1], results[2])

axelrod/tests/integration/test_tournament.py

@@ -1,6 +1,7 @@
 import unittest
 import axelrod
 import tempfile
+import filecmp
 
 from axelrod.strategy_transformers import FinalTransformer
 
@@ -60,6 +61,39 @@ def test_parallel_play(self):
         actual_outcome = sorted(zip(self.player_names, scores))
         self.assertEqual(actual_outcome, self.expected_outcome)
 
+    def test_repeat_tournament_deterministic(self):
+        """A test to check that tournament gives same results."""
+        deterministic_players = [s() for s in axelrod.ordinary_strategies
+                                 if not s().classifier['stochastic']]
+        files = []
+        for _ in range(2):
+            tournament = axelrod.Tournament(name='test',
+                                            players=deterministic_players,
+                                            game=self.game, turns=2,
+                                            repetitions=2)
+            files.append(tempfile.NamedTemporaryFile())
+            tournament.play(progress_bar=False, filename=files[-1].name,
+                            build_results=False)
+        self.assertTrue(filecmp.cmp(files[0].name, files[1].name))
+
+    def test_repeat_tournament_stochastic(self):
+        """
+        A test to check that tournament gives same results when setting seed.
+        """
+        files = []
+        for _ in range(2):
+            axelrod.set_seed(0)
+            stochastic_players = [s() for s in axelrod.ordinary_strategies
+                                  if s().classifier['stochastic']]
+            tournament = axelrod.Tournament(name='test',
+                                            players=stochastic_players,
+                                            game=self.game, turns=2,
+                                            repetitions=2)
+            files.append(tempfile.NamedTemporaryFile())
+            tournament.play(progress_bar=False, filename=files[-1].name,
+                            build_results=False)
+        self.assertTrue(filecmp.cmp(files[0].name, files[1].name))
+
 
 class TestNoisyTournament(unittest.TestCase):
     def test_noisy_tournament(self):

axelrod/tests/unit/test_random_.py

@@ -1,9 +1,10 @@
 """Test for the random strategy."""
 
+import numpy
 import random
 import unittest
 
-from axelrod import random_choice, Actions
+from axelrod import random_choice, set_seed, Actions
 
 C, D = Actions.C, Actions.D
 
@@ -16,3 +17,18 @@ def test_return_values(self):
         self.assertEqual(random_choice(), C)
         random.seed(2)
         self.assertEqual(random_choice(), D)
+
+    def test_set_seed(self):
+        """Test that numpy and stdlib random seed is set by set seed helper
+        function"""
+
+        numpy_random_numbers = []
+        stdlib_random_numbers = []
+        for _ in range(2):
+            set_seed(0)
+            numpy_random_numbers.append(numpy.random.random())
+            stdlib_random_numbers.append(random.random())
+
+        self.assertEqual(numpy_random_numbers[0], numpy_random_numbers[1])
+        self.assertEqual(stdlib_random_numbers[0], stdlib_random_numbers[1])
+

docs/tutorials/advanced/index.rst

@@ -13,3 +13,4 @@ Contents:
    making_tournaments.rst
    reading_and_writing_interactions.rst
    using_the_cache.rst
+   setting_a_seed.rst

docs/tutorials/advanced/setting_a_seed.rst

@@ -0,0 +1,35 @@
+.. _setting_a_seed:
+
+Setting a random seed
+=====================
+
+The library has a variety of strategies whose behaviour is stochastic. To ensure
+reproducible results a random seed should be set. As both Numpy and the standard
+library are used for random number generation, both seeds need to be
+set. To do this we can use the `set_seed` function::
+
+    >>> import axelrod as axl
+    >>> players = (axl.Random(), axl.MetaMixer())  # Two stochastic strategies
+    >>> axl.set_seed(0)
+    >>> axl.Match(players, turns=3).play()
+    [('D', 'C'), ('D', 'D'), ('C', 'D')]
+
+We obtain the same results is it is played with the same seed::
+
+    >>> axl.set_seed(0)
+    >>> axl.Match(players, turns=3).play()
+    [('D', 'C'), ('D', 'D'), ('C', 'D')]
+
+Note that this is equivalent to::
+
+    >>> import numpy
+    >>> import random
+    >>> players = (axl.Random(), axl.MetaMixer())
+    >>> random.seed(0)
+    >>> numpy.random.seed(0)
+    >>> axl.Match(players, turns=3).play()
+    [('D', 'C'), ('D', 'D'), ('C', 'D')]
+    >>> numpy.random.seed(0)
+    >>> random.seed(0)
+    >>> axl.Match(players, turns=3).play()
+    [('D', 'C'), ('D', 'D'), ('C', 'D')]