Merge pull request #139 from ImogenBits/bugfix

Fix default scoring function if generator's Solution score is 0

algobattle/problem.py

@@ -209,7 +209,9 @@ def default_score(
         try:
             return max(0, min(1, sol_score / gen_score))
         except ZeroDivisionError:
-            return float(sol_score < 0)
+            # if generator scored 0 then the solver will have achieved an equal or better score
+            # i.e. the Fight's score is simply 1 regardless of its solution score.
+            return 1
     else:
         return max(0, min(1, solution.score(instance, Role.solver)))
 

tests/test_util.py

@@ -1,7 +1,23 @@
 """Tests for all util functions."""
+from math import inf
 import unittest
 
 from algobattle.battle import Battle, Iterated, Averaged
+from algobattle.problem import InstanceModel, SolutionModel, default_score
+from algobattle.util import Role
+
+
+class DummyInstance(InstanceModel):  # noqa: D101
+    @property
+    def size(self) -> int:
+        return 1
+
+
+class DummySolution(SolutionModel[DummyInstance]):  # noqa: D101
+    val: float
+
+    def score(self, instance: DummyInstance, role: Role) -> float:
+        return self.val
 
 
 class Utiltests(unittest.TestCase):
@@ -12,6 +28,35 @@ def test_default_battle_types(self):
         self.assertEqual(Battle.all()["Iterated"], Iterated)
         self.assertEqual(Battle.all()["Averaged"], Averaged)
 
+    def test_default_fight_score(self):
+        """Tests the default fight scoring function."""
+        instance = DummyInstance()
+        scores = [
+            (0, 0, 1),
+            (0, 2, 1),
+            (0, 4, 1),
+            (0, inf, 1),
+            (2, 0, 0),
+            (2, 2, 1),
+            (2, 4, 1),
+            (2, inf, 1),
+            (4, 0, 0),
+            (4, 2, 0.5),
+            (4, 4, 1),
+            (4, inf, 1),
+            (inf, 0, 0),
+            (inf, 2, 0),
+            (inf, 4, 0),
+            (inf, inf, 1),
+        ]
+        for gen, sol, score in scores:
+            self.assertEqual(
+                default_score(
+                    instance, generator_solution=DummySolution(val=gen), solver_solution=DummySolution(val=sol)
+                ),
+                score,
+            )
+
 
 if __name__ == "__main__":
     unittest.main()