Fix regression in action graph games

ChangeLog

@@ -1,5 +1,12 @@
 # Changelog
 
+## [16.7.0] - unreleased
+
+### Fixed
+- Corrected a regression in action graph games that left the internal data structure not fully initialised,
+  leading to segmentation faults.
+
+
 ## [16.6.0] - 2026-03-24
 
 ### Changed

src/games/gameagg.cc

@@ -186,6 +186,7 @@ GameAGGRep::GameAGGRep(std::shared_ptr<agg::AGG> p_aggPtr) : aggPtr(p_aggPtr)
                     s->m_label = std::to_string(st++);
                   });
   }
+  IndexStrategies();
 }
 
 Game GameAGGRep::Copy() const

src/games/gamebagg.cc

@@ -223,6 +223,7 @@ GameBAGGRep::GameBAGGRep(std::shared_ptr<agg::BAGG> _baggPtr)
                     });
     }
   }
+  IndexStrategies();
 }
 
 Game GameBAGGRep::Copy() const

src/pygambit/gambit.pxd

@@ -249,7 +249,8 @@ cdef extern from "games/game.h":
             iterator begin() except +
             iterator end() except +
 
-        int IsTree() except +
+        bool IsTree() except +
+        bool IsAgg() except +
 
         string GetTitle() except +
         void SetTitle(string) except +

src/pygambit/game.pxi

@@ -858,8 +858,8 @@ class Game:
                 self.game.deref().GetPlayer(pl+1).deref().GetStrategy(st+1)
             )
 
-        if self.is_tree:
-            return TreeGameOutcome.wrap(self.game, psp)
+        if self.is_tree or self.game.deref().IsAgg():
+            return DerivedGameOutcome.wrap(self.game, psp)
         else:
             outcome = Outcome.wrap(deref(deref(psp).deref()).GetOutcome())
             if outcome.outcome != cython.cast(c_GameOutcome, NULL):

src/pygambit/outcome.pxi

@@ -126,8 +126,10 @@ class Outcome:
 
 
 @cython.cclass
-class TreeGameOutcome:
-    """Represents an outcome in a strategic game derived from an extensive game."""
+class DerivedGameOutcome:
+    """Represents an outcome in a strategic game derived from a game in another representation.
+    Such outcomes are one-to-one with the set of pure strategy profiles.
+    """
     c_game = cython.declare(c_Game)
     psp = cython.declare(shared_ptr[c_PureStrategyProfile])
 
@@ -136,8 +138,8 @@ class TreeGameOutcome:
 
     @staticmethod
     @cython.cfunc
-    def wrap(game: c_Game, psp: shared_ptr[c_PureStrategyProfile]) -> TreeGameOutcome:
-        obj: TreeGameOutcome = TreeGameOutcome.__new__(TreeGameOutcome)
+    def wrap(game: c_Game, psp: shared_ptr[c_PureStrategyProfile]) -> DerivedGameOutcome:
+        obj: DerivedGameOutcome = DerivedGameOutcome.__new__(DerivedGameOutcome)
         obj.c_game = game
         obj.psp = psp
         return obj
@@ -152,8 +154,8 @@ class TreeGameOutcome:
 
     def __eq__(self, other: typing.Any) -> bool:
         return (
-            isinstance(other, TreeGameOutcome) and
-            deref(self.psp).deref() == deref(cython.cast(TreeGameOutcome, other).psp).deref()
+            isinstance(other, DerivedGameOutcome) and
+            deref(self.psp).deref() == deref(cython.cast(DerivedGameOutcome, other).psp).deref()
         )
 
     def __getitem__(self, player: Player | str) -> Rational:

tests/games.py

@@ -14,6 +14,8 @@ def read_from_file(fn: str) -> gbt.Game:
         return gbt.read_efg(pathlib.Path("tests/test_games") / fn)
     elif fn.endswith(".nfg"):
         return gbt.read_nfg(pathlib.Path("tests/test_games") / fn)
+    elif fn.endswith(".agg"):
+        return gbt.read_agg(pathlib.Path("tests/test_games") / fn)
     else:
         raise ValueError(f"Unknown file extension in {fn}")
 

tests/test_nash.py

@@ -159,6 +159,19 @@ class QREquilibriumTestCase:
         marks=pytest.mark.nash_enumpure_strategy,
         id="test_enumpure_8",
     ),
+    # Action graph game
+    pytest.param(
+        EquilibriumTestCase(
+            factory=functools.partial(games.read_from_file, "2x2.agg"),
+            solver=functools.partial(gbt.nash.enumpure_solve),
+            expected=[
+                [d(1, 0), d(1, 0)],
+                [d(0, 1), d(0, 1)],
+            ],
+        ),
+        marks=pytest.mark.nash_enumpure_strategy,
+        id="test_enumpure_9",
+    ),
 ]
 
 
@@ -232,6 +245,23 @@ class QREquilibriumTestCase:
         marks=pytest.mark.nash_enummixed_strategy,
         id="test_enumixed_rational_5",
     ),
+    # Action graph game
+    pytest.param(
+        EquilibriumTestCase(
+            factory=functools.partial(games.read_from_file, "2x2.agg"),
+            solver=functools.partial(gbt.nash.enummixed_solve, rational=True),
+            expected=[
+                [d(1, 0), d(1, 0)],
+                [d(0, 1), d(0, 1)],
+                [
+                    d("4186770418979088/4641467073735727", "454696654756639/4641467073735727"),
+                    d("4186770418979088/4641467073735727", "454696654756639/4641467073735727"),
+                ],
+            ],
+        ),
+        marks=pytest.mark.nash_enummixed_strategy,
+        id="test_enummixed_rational_6",
+    ),
 ]
 
 
@@ -589,6 +619,25 @@ class QREquilibriumTestCase:
         marks=pytest.mark.nash_lcp_strategy,
         id="test_lcp_strategy_rational_11",
     ),
+    # Action graph game
+    pytest.param(
+        EquilibriumTestCase(
+            factory=functools.partial(games.read_from_file, "2x2.agg"),
+            solver=functools.partial(
+                gbt.nash.lcp_solve, rational=True, use_strategic=True, stop_after=None
+            ),
+            expected=[
+                [d(1, 0), d(1, 0)],
+                [
+                    d("4186770418979088/4641467073735727", "454696654756639/4641467073735727"),
+                    d("4186770418979088/4641467073735727", "454696654756639/4641467073735727"),
+                ],
+                [d(0, 1), d(0, 1)],
+            ],
+        ),
+        marks=pytest.mark.nash_lcp_strategy,
+        id="test_lcp_strategy_rational_12",
+    ),
 ]
 
 
@@ -2158,16 +2207,13 @@ def test_nash_strategy_solver_w_start(test_case: EquilibriumTestCaseWithStart, s
     # 3-player perfect info game to test behavior two off equilibrium path
     pytest.param(
         EquilibriumTestCase(
-            factory=functools.partial(
-                games.read_from_file, "3_player_PI_2_dev_off_eq_path.efg"
-            ),
+            factory=functools.partial(games.read_from_file, "3_player_PI_2_dev_off_eq_path.efg"),
             solver=functools.partial(gbt.nash.enumpoly_solve, stop_after=None),
             expected=[
                 # candidate,10,10,1000,10000
                 [[d(1, 0)], [d(1, 0), d(1, 0, 0, 0)], [d(1, 0, 0, 0, 0)]],
                 # candidate,01,00,0000,00000
-                [[d(0, 1)], [d(1, 0), d(1, 0, 0, 0)],
-                 [d(1, 0, 0, 0, 0)]],
+                [[d(0, 1)], [d(1, 0), d(1, 0, 0, 0)], [d(1, 0, 0, 0, 0)]],
             ],
             regret_tol=TOL,
             prob_tol=TOL,
@@ -2177,9 +2223,7 @@ def test_nash_strategy_solver_w_start(test_case: EquilibriumTestCaseWithStart, s
     ),
     pytest.param(
         EquilibriumTestCase(
-            factory=functools.partial(
-                games.read_from_file, "3_player_PI_2_dev_off_eq_path.efg"
-            ),
+            factory=functools.partial(games.read_from_file, "3_player_PI_2_dev_off_eq_path.efg"),
             solver=functools.partial(gbt.nash.enumpoly_solve, stop_after=None),
             expected=[
                 [[d(1, 0)], [d(1, 0), d(1, 0, 0, 0)], [d(1, 0, 0, 0, 0)]],