Merge pull request #382 from QuantEcon/payoff_arrays

NormalFormGame: Add `payoff_arrays` attribute
QuantEcon · Jan 9, 2018 · d73c959 · d73c959
2 parents e61702f + e439ba8
commit d73c959
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Showing 3 changed files with 26 additions and 10 deletions.
diff --git a/quantecon/game_theory/lemke_howson.py b/quantecon/game_theory/lemke_howson.py
@@ -125,7 +125,7 @@ def lemke_howson(g, init_pivot=0, max_iter=10**6, capping=None,
     if N != 2:
         raise NotImplementedError('Implemented only for 2-player games')
 
-    payoff_matrices = tuple(g.players[i].payoff_array for i in range(N))
+    payoff_matrices = g.payoff_arrays
     nums_actions = g.nums_actions
     total_num = sum(nums_actions)
 

diff --git a/quantecon/game_theory/normal_form_game.py b/quantecon/game_theory/normal_form_game.py
@@ -486,6 +486,9 @@ class NormalFormGame:
     nums_actions : tuple(int)
         Tuple of the numbers of actions, one for each player.
 
+    payoff_arrays : tuple(ndarray(float, ndim=N))
+        Tuple of the payoff arrays, one for each player.
+
     """
     def __init__(self, data, dtype=None):
         # data represents an array_like of Players
@@ -575,6 +578,9 @@ def __init__(self, data, dtype=None):
         self.nums_actions = tuple(
             player.num_actions for player in self.players
         )
+        self.payoff_arrays = tuple(
+            player.payoff_array for player in self.players
+        )
 
     @property
     def payoff_profile_array(self):

diff --git a/quantecon/game_theory/tests/test_normal_form_game.py b/quantecon/game_theory/tests/test_normal_form_game.py
@@ -166,18 +166,28 @@ class TestNormalFormGame_Asym2p:
 
     def setUp(self):
         """Setup a NormalFormGame instance"""
-        matching_pennies_bimatrix = [[(1, -1), (-1, 1)],
-                                     [(-1, 1), (1, -1)]]
-        self.g = NormalFormGame(matching_pennies_bimatrix)
+        self.BoS_bimatrix = np.array([[(3, 2), (1, 1)],
+                                      [(0, 0), (2, 3)]])
+        self.g = NormalFormGame(self.BoS_bimatrix)
 
     def test_getitem(self):
-        assert_array_equal(self.g[1, 0], [-1, 1])
+        action_profile = (1, 0)
+        assert_array_equal(self.g[action_profile],
+                           self.BoS_bimatrix[action_profile])
 
-    def test_is_nash_against_pure(self):
-        ok_(not self.g.is_nash((0, 0)))
+    def test_is_nash_pure(self):
+        ok_(not self.g.is_nash((1, 0)))
+
+    def test_is_nash_mixed(self):
+        ok_(self.g.is_nash(([3/4, 1/4], [1/4, 3/4])))
 
-    def test_is_nash_against_mixed(self):
-        ok_(self.g.is_nash(([1/2, 1/2], [1/2, 1/2])))
+    def test_payoff_arrays(self):
+        assert_array_equal(
+            self.g.payoff_arrays[0], self.BoS_bimatrix[:, :, 0]
+        )
+        assert_array_equal(
+            self.g.payoff_arrays[1], self.BoS_bimatrix[:, :, 1].T
+        )
 
 
 class TestNormalFormGame_3p:
@@ -349,7 +359,7 @@ def test_normalformgame_setitem_1p():
     eq_(g.players[0].payoff_array[0], 10)
 
 
-# Test __repre__ #
+# Test __repr__ #
 
 def test_player_repr():
     nums_actions = (2, 3, 4)