Test that we get the same solution if we solve the same game twice.

diff --git a/TODO b/TODO
index 2fe7ea4eab6b3fc44b571c8dcdb1272c6a4e153e..e8bf9e55b3f09348b157b6dd295fb18442542cbc 100644 (file)
--- a/TODO
+++ b/TODO
@@ -7,6 +7,3 @@
 
 4. Come up with a fast heuristic (like making nu huge and taking e1 as
    our point) that finds a primal feasible point.
-
-5. Add a test to ensure that if we solve the same game twice, we get the
-   same answer back.

diff --git a/test/symmetric_linear_game_test.py b/test/symmetric_linear_game_test.py
index f3aef71376aeb3f5a974d38d0171d6e92711a317..887831a44a68aeae7e8b25514154cfbe53f0309c 100644 (file)
--- a/test/symmetric_linear_game_test.py
+++ b/test/symmetric_linear_game_test.py
@@ -5,7 +5,7 @@ Unit tests for the :class:`SymmetricLinearGame` class.
 from unittest import TestCase
 
 from dunshire.games import SymmetricLinearGame
-from dunshire.matrices import eigenvalues_re, inner_product
+from dunshire.matrices import eigenvalues_re, inner_product, norm
 from dunshire import options
 from .randomgen import (random_icecream_game, random_ll_icecream_game,
                         random_ll_orthant_game, random_nn_scaling,
@@ -42,6 +42,24 @@ class SymmetricLinearGameTest(TestCase): # pylint: disable=R0904
         self.assertTrue(abs(first - second) < options.ABS_TOL*modifier)
 
 
+    def test_solutions_dont_change(self):
+        """
+        If we solve the same problem twice, we should get
+        the same answer both times.
+        """
+        G = random_orthant_game()
+        soln1 = G.solution()
+        soln2 = G.solution()
+        p1_diff = norm(soln1.player1_optimal() - soln2.player1_optimal())
+        p2_diff = norm(soln1.player2_optimal() - soln2.player2_optimal())
+        gv_diff = abs(soln1.game_value() - soln2.game_value())
+
+        p1_close = p1_diff < options.ABS_TOL
+        p2_close = p2_diff < options.ABS_TOL
+        gv_close = gv_diff < options.ABS_TOL
+
+        self.assertTrue(p1_close and p2_close and gv_close)
+
 
     def test_condition_lower_bound(self):
         """