Refactored games to generalise & add asymmetric games (#1413)

* Added asymmetric games and made regular games a subclass

* small improvements to code style

* fixing docs mock...

* Revert "fixing docs mock..."

This reverts commit 09fb251.

* used IntEnum to simplify

* small improvements & a fix

* added asymmetric games to docs

* added werror if invalid payoff matrices are given

* removed .item()

* changed dbs.action_to_int to use IntEnum behaviour

* Revert "changed dbs.action_to_int to use IntEnum behaviour"

This reverts commit bb6171c.

* made library code more robust wrt integer actions

* all strategies now work with integer actions

* added tests and fixed __eq__

* improved coverage

* changed Action back to Enum and added casting to score

* added casting test

* removed numpy mocking

* changed doc due to doctests being picky

* re-fixed doctest examples

* review changes

* Added tutorial for implementing new games

* fixed formatting

* made doctests work

.github/workflows/config.yml

@@ -38,6 +38,7 @@ jobs:
         python -m pip install sphinx
         python -m pip install sphinx_rtd_theme
         python -m pip install mock
+        python -m pip install numpy
         cd docs; make clean; make html; cd ..;
     - name: Run doctests
       run: |

axelrod/__init__.py

@@ -16,7 +16,7 @@
 from axelrod.load_data_ import load_pso_tables, load_weights
 from axelrod import graph
 from axelrod.plot import Plot
-from axelrod.game import DefaultGame, Game
+from axelrod.game import DefaultGame, AsymmetricGame, Game
 from axelrod.history import History, LimitedHistory
 from axelrod.player import Player
 from axelrod.classifier import Classifiers

axelrod/game.py

@@ -1,4 +1,7 @@
 from typing import Tuple, Union
+from enum import Enum
+
+import numpy as np
 
 from axelrod import Action
 
@@ -7,7 +10,7 @@
 Score = Union[int, float]
 
 
-class Game(object):
+class AsymmetricGame(object):
     """Container for the game matrix and scoring logic.
 
     Attributes
@@ -16,9 +19,85 @@ class Game(object):
         The numerical score attribute to all combinations of action pairs.
     """
 
-    def __init__(
-        self, r: Score = 3, s: Score = 0, t: Score = 5, p: Score = 1
-    ) -> None:
+    # pylint: disable=invalid-name
+    def __init__(self, A: np.array, B: np.array) -> None:
+        """
+        Creates an asymmetric game from two matrices.
+
+        Parameters
+        ----------
+        A: np.array
+            the payoff matrix for player A.
+        B: np.array
+            the payoff matrix for player B.
+        """
+
+        if A.shape != B.transpose().shape:
+            raise ValueError(
+                "AsymmetricGame was given invalid payoff matrices; the shape "
+                "of matrix A should be the shape of B's transpose matrix."
+            )
+
+        self.A = A
+        self.B = B
+
+        self.scores = {
+            pair: self.score(pair) for pair in ((C, C), (D, D), (C, D), (D, C))
+        }
+
+    def score(
+        self, pair: Union[Tuple[Action, Action], Tuple[int, int]]
+    ) -> Tuple[Score, Score]:
+        """Returns the appropriate score for a decision pair.
+        Parameters
+        ----------
+        pair: tuple(int, int) or tuple(Action, Action)
+            A pair of actions for two players, for example (0, 1) corresponds
+            to the row player choosing their first action and the column
+            player choosing their second action; in the prisoners' dilemma,
+            this is equivalent to player 1 cooperating and player 2 defecting.
+            Can also be a pair of Actions, where C corresponds to '0'
+            and D to '1'.
+
+        Returns
+        -------
+        tuple of int or float
+            Scores for two player resulting from their actions.
+        """
+
+        # if an Action has been passed to the method,
+        # get which integer the Action corresponds to
+        def get_value(x):
+            if isinstance(x, Enum):
+                return x.value
+            return x
+        row, col = map(get_value, pair)
+
+        return (self.A[row][col], self.B[row][col])
+
+    def __repr__(self) -> str:
+        return "Axelrod game with matrices: {}".format((self.A, self.B))
+
+    def __eq__(self, other):
+        if not isinstance(other, AsymmetricGame):
+            return False
+        return self.A.all() == other.A.all() and self.B.all() == other.B.all()
+
+
+class Game(AsymmetricGame):
+    """
+    Simplification of the AsymmetricGame class for symmetric games.
+    Takes advantage of Press and Dyson notation.
+
+    Can currently only be 2x2.
+
+    Attributes
+    ----------
+    scores: dict
+        The numerical score attribute to all combinations of action pairs.
+    """
+
+    def __init__(self, r: Score = 3, s: Score = 0, t: Score = 5, p: Score = 1) -> None:
         """Create a new game object.
 
         Parameters
@@ -32,12 +111,9 @@ def __init__(
         p: int or float
             Score obtained by both player for mutual defection.
         """
-        self.scores = {
-            (C, C): (r, r),
-            (D, D): (p, p),
-            (C, D): (s, t),
-            (D, C): (t, s),
-        }
+        A = np.array([[r, s], [t, p]])
+
+        super().__init__(A, A.transpose())
 
     def RPST(self) -> Tuple[Score, Score, Score, Score]:
         """Returns game matrix values in Press and Dyson notation."""
@@ -47,21 +123,6 @@ def RPST(self) -> Tuple[Score, Score, Score, Score]:
         T = self.scores[(D, C)][0]
         return R, P, S, T
 
-    def score(self, pair: Tuple[Action, Action]) -> Tuple[Score, Score]:
-        """Returns the appropriate score for a decision pair.
-
-        Parameters
-        ----------
-        pair: tuple(Action, Action)
-            A pair actions for two players, for example (C, C).
-
-        Returns
-        -------
-        tuple of int or float
-            Scores for two player resulting from their actions.
-        """
-        return self.scores[pair]
-
     def __repr__(self) -> str:
         return "Axelrod game: (R,P,S,T) = {}".format(self.RPST())
 

axelrod/history.py

@@ -130,12 +130,10 @@ def flip_plays(self):
     def append(self, play, coplay):
         """Appends a new (play, coplay) pair an updates metadata for
         number of cooperations and defections, and the state distribution."""
-
         self._plays.append(play)
         self._actions[play] += 1
-        if coplay:
-            self._coplays.append(coplay)
-            self._state_distribution[(play, coplay)] += 1
+        self._coplays.append(coplay)
+        self._state_distribution[(play, coplay)] += 1
         if len(self._plays) > self.memory_depth:
             first_play, first_coplay = self._plays.pop(0), self._coplays.pop(0)
             self._actions[first_play] -= 1

axelrod/tests/property.py

@@ -11,6 +11,7 @@
     lists,
     sampled_from,
 )
+from hypothesis.extra.numpy import arrays
 
 
 @composite
@@ -381,3 +382,16 @@ def games(draw, prisoners_dilemma=True, max_value=100):
 
     game = axl.Game(r=r, s=s, t=t, p=p)
     return game
+
+
+@composite
+def asymmetric_games(draw, valid=True):
+    """Hypothesis decorator to draw a random asymmetric game."""
+
+    rows = draw(integers(min_value=2, max_value=255))
+    cols = draw(integers(min_value=2, max_value=255))
+
+    A = draw(arrays(int, (rows, cols)))
+    B = draw(arrays(int, (cols, rows)))
+
+    return axl.AsymmetricGame(A, B)

axelrod/tests/unit/test_game.py

@@ -1,9 +1,13 @@
 import unittest
 
+import numpy as np
+
 import axelrod as axl
-from axelrod.tests.property import games
+from axelrod.tests.property import games, asymmetric_games
 from hypothesis import given, settings
 from hypothesis.strategies import integers
+from hypothesis.extra.numpy import arrays, array_shapes
+
 
 C, D = axl.Action.C, axl.Action.D
 
@@ -77,3 +81,50 @@ def test_random_repr(self, game):
         expected_repr = "Axelrod game: (R,P,S,T) = {}".format(game.RPST())
         self.assertEqual(expected_repr, game.__repr__())
         self.assertEqual(expected_repr, str(game))
+
+    @given(game=games())
+    def test_integer_actions(self, game):
+        """Test Actions and integers are treated equivalently."""
+        pair_ints = {
+            (C, C): (0 ,0),
+            (C, D): (0, 1),
+            (D, C): (1, 0),
+            (D, D): (1, 1)
+        }
+        for key, value in pair_ints.items():
+            self.assertEqual(game.score(key), game.score(value))
+
+class TestAsymmetricGame(unittest.TestCase):
+    @given(A=arrays(int, array_shapes(min_dims=2, max_dims=2, min_side=2)),
+           B=arrays(int, array_shapes(min_dims=2, max_dims=2, min_side=2)))
+    @settings(max_examples=5)
+    def test_invalid_matrices(self, A, B):
+        """Test that an error is raised when the matrices aren't the right size."""
+        # ensures that an error is raised when the shapes are invalid,
+        # and not raised otherwise
+        error_raised = False
+        try:
+            game = axl.AsymmetricGame(A, B)
+        except ValueError:
+            error_raised = True
+
+        self.assertEqual(error_raised, (A.shape != B.transpose().shape))
+
+    @given(asymgame=asymmetric_games())
+    @settings(max_examples=5)
+    def test_random_repr(self, asymgame):
+        """Test repr with random scores."""
+        expected_repr = "Axelrod game with matrices: {}".format((asymgame.A, asymgame.B))
+        self.assertEqual(expected_repr, asymgame.__repr__())
+        self.assertEqual(expected_repr, str(asymgame))
+
+    @given(asymgame1=asymmetric_games(),
+           asymgame2=asymmetric_games())
+    @settings(max_examples=5)
+    def test_equality(self, asymgame1, asymgame2):
+        """Tests equality of AsymmetricGames based on their matrices."""
+        self.assertFalse(asymgame1=='foo')
+        self.assertEqual(asymgame1, asymgame1)
+        self.assertEqual(asymgame2, asymgame2)
+        self.assertEqual((asymgame1==asymgame2), (asymgame1.A.all() == asymgame2.A.all()
+                                                  and asymgame1.B.all() == asymgame2.B.all()))

docs/conf.py

@@ -26,9 +26,6 @@
     "matplotlib.transforms",
     "mpl_toolkits.axes_grid1",
     "multiprocess",
-    "numpy",
-    "numpy.linalg",
-    "numpy.random",
     "pandas",
     "pandas.util",
     "pandas.util.decorators",

docs/how-to/use_different_stage_games.rst

@@ -1,3 +1,5 @@
+.. _use_different_stage_games:
+
 Use different stage games
 =========================
 
@@ -47,3 +49,38 @@ The default Prisoner's dilemma has different results::
     >>> results = tournament.play()
     >>> results.ranked_names
     ['Defector', 'Tit For Tat', 'Cooperator']
+
+Asymmetric games can also be implemented via the AsymmetricGame class 
+with two Numpy arrays for payoff matrices::
+
+    >>> import numpy as np
+    >>> A = np.array([[3, 1], [1, 3]])
+    >>> B = np.array([[1, 3], [2, 1]])
+    >>> asymmetric_game = axl.AsymmetricGame(A, B)
+    >>> asymmetric_game  # doctest: +NORMALIZE_WHITESPACE
+    Axelrod game with matrices: (array([[3, 1],
+                                        [1, 3]]),
+                                 array([[1, 3],
+                                        [2, 1]]))
+
+Asymmetric games can also be different sizes (even if symmetric; regular games
+can currently only be 2x2), such as Rock Paper Scissors::
+
+    >>> A = np.array([[0, -1, 1], [1, 0, -1], [-1, 1, 0]])
+    >>> rock_paper_scissors = axl.AsymmetricGame(A, -A)
+    >>> rock_paper_scissors  # doctest: +NORMALIZE_WHITESPACE
+    Axelrod game with matrices: (array([[ 0, -1,  1],
+                                        [ 1,  0, -1],
+                                        [-1,  1,  0]]),
+                                 array([[ 0,  1, -1],
+                                        [-1,  0,  1],
+                                        [ 1, -1,  0]]))
+
+**NB: Some features of Axelrod, such as strategy transformers, are specifically created for
+use with the iterated Prisoner's Dilemma; they may break with games of other sizes.**
+Note also that most strategies in Axelrod are Prisoners' Dilemma strategies, so behave
+as though they are playing the Prisoners' Dilemma; in the rock-paper-scissors example above,
+they will certainly never choose scissors (because their strategy action set is two actions!)
+
+For a more detailed tutorial on how to implement another game into Axelrod, :ref:`here is a 
+tutorial using rock paper scissors as an example. <implement-new-games>`