X-Git-Url: https://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2Fdunshire%2Fgames.py;h=65fc791b20bd0624ee714a724581eb1537fa2edf;hb=d1638062ec3a28dc64b91f308858211db243db7b;hp=76fbf7deedfec733bf4213bec000bdf449087e75;hpb=9da611019b85e58ecab8450f9a9043c6f4a184d1;p=dunshire.git

diff --git a/src/dunshire/games.py b/src/dunshire/games.py
index 76fbf7d..65fc791 100644
--- a/src/dunshire/games.py
+++ b/src/dunshire/games.py
@@ -504,7 +504,7 @@ class SymmetricLinearGame:
 
 
 
-def _random_square_matrix(dims):
+def _random_matrix(dims):
     """
     Generate a random square (``dims``-by-``dims``) matrix,
     represented as a list of rows. This is used only by the
@@ -512,6 +512,23 @@ def _random_square_matrix(dims):
     """
     return [[uniform(-10, 10) for i in range(dims)] for j in range(dims)]
 
+def _random_nonnegative_matrix(dims):
+    """
+    Generate a random square (``dims``-by-``dims``) matrix with
+    nonnegative entries, represented as a list of rows. This is used
+    only by the :class:`SymmetricLinearGameTest` class.
+    """
+    L = _random_matrix(dims)
+    return [[abs(entry) for entry in row] for row in L]
+
+def _random_diagonal_matrix(dims):
+    """
+    Generate a random square (``dims``-by-``dims``) matrix with nonzero
+    entries only on the diagonal, represented as a list of rows. This is
+    used only by the :class:`SymmetricLinearGameTest` class.
+    """
+    return [[uniform(-10, 10)*int(i == j) for i in range(dims)]
+            for j in range(dims)]
 
 def _random_orthant_params():
     """
@@ -523,7 +540,7 @@ def _random_orthant_params():
     K = NonnegativeOrthant(ambient_dim)
     e1 = [uniform(0.5, 10) for idx in range(K.dimension())]
     e2 = [uniform(0.5, 10) for idx in range(K.dimension())]
-    L = _random_square_matrix(K.dimension())
+    L = _random_matrix(K.dimension())
     return (L, K, e1, e2)
 
 
@@ -550,7 +567,7 @@ def _random_icecream_params():
     fudge_factor = 1.0 / (2.0*sqrt(K.dimension() - 1.0))
     e1 += [fudge_factor*uniform(0, 1) for idx in range(K.dimension() - 1)]
     e2 += [fudge_factor*uniform(0, 1) for idx in range(K.dimension() - 1)]
-    L = _random_square_matrix(K.dimension())
+    L = _random_matrix(K.dimension())
 
     return (L, K, e1, e2)
 
@@ -804,3 +821,20 @@ class SymmetricLinearGameTest(TestCase):
         """
         (L, K, e1, e2) = _random_icecream_params()
         self.assert_orthogonality(L, K, e1, e2)
+
+
+    def test_positive_operator_value(self):
+        """
+        Test that a positive operator on the nonnegative orthant gives
+        rise to a a game with a nonnegative value.
+
+        This test theoretically applies to the ice-cream cone as well,
+        but we don't know how to make positive operators on that cone.
+        """
+        (_, K, e1, e2) = _random_orthant_params()
+
+        # Ignore that L, we need a nonnegative one.
+        L = _random_nonnegative_matrix(K.dimension())
+
+        game = SymmetricLinearGame(L, K, e1, e2)
+        self.assertTrue(game.solution().game_value() >= -options.ABS_TOL)