fix: retain restored feature statistics during database construction

openevolve/database.py

@@ -30,7 +30,7 @@
     ProgramState,
 )
 from openevolve.utils.code_utils import calculate_edit_distance
-from openevolve.utils.metrics_utils import safe_numeric_average, get_fitness_score
+from openevolve.utils.metrics_utils import get_fitness_score, safe_numeric_average
 
 logger = logging.getLogger(__name__)
 
@@ -186,6 +186,9 @@ def __init__(
         # Track the last iteration number (for resuming)
         self.last_iteration: int = 0
 
+        # Initialize before loading so restored MAP-Elites scales are retained.
+        self.feature_stats: Dict[str, Dict[str, Union[float, float, List[float]]]] = {}
+
         # Load database from disk if path is provided
         if config.db_path and os.path.exists(config.db_path):
             self.load(config.db_path)
@@ -211,7 +214,6 @@ def __init__(
         self.diversity_reference_size: int = getattr(config, "diversity_reference_size", 20)
 
         # Feature scaling infrastructure
-        self.feature_stats: Dict[str, Dict[str, Union[float, float, List[float]]]] = {}
         self.feature_scaling_method: str = "minmax"  # Options: minmax, zscore, percentile
 
         # Per-dimension bins support
@@ -1136,6 +1138,7 @@ def _llm_judge_novelty(self, program: Program, similar_program: Program) -> bool
         Use LLM to judge if a program is novel compared to a similar existing program
         """
         import asyncio
+
         from openevolve.novelty_judge import NOVELTY_SYSTEM_MSG, NOVELTY_USER_MSG
 
         user_msg = NOVELTY_USER_MSG.format(

tests/test_constructor_feature_stats.py

@@ -0,0 +1,45 @@
+"""Loading through db_path must retain the checkpoint's MAP-Elites scale."""
+
+import tempfile
+import unittest
+
+from openevolve.config import DatabaseConfig
+from openevolve.database import Program, ProgramDatabase
+
+
+class TestConstructorFeatureStats(unittest.TestCase):
+    def setUp(self):
+        self.tempdir = tempfile.TemporaryDirectory()
+        self.addCleanup(self.tempdir.cleanup)
+        self.config = DatabaseConfig(
+            in_memory=True,
+            num_islands=1,
+            feature_dimensions=["custom"],
+            feature_bins=10,
+            archive_size=1,
+        )
+        self.db = ProgramDatabase(self.config)
+        self.db._update_feature_stats("custom", 0.0)
+        self.db._update_feature_stats("custom", 100.0)
+        self.program = Program(
+            id="candidate", code="pass", metrics={"combined_score": 0.5, "custom": 25.0}
+        )
+        self.db.add(self.program)
+        self.db.save(self.tempdir.name)
+        self.config.db_path = self.tempdir.name
+
+    def test_constructor_preserves_loaded_feature_ranges(self):
+        restored = ProgramDatabase(self.config)
+        self.assertEqual(restored.feature_stats, self.db.feature_stats)
+
+    def test_constructor_preserves_feature_placement_without_second_load(self):
+        expected = self.db._calculate_feature_coords(self.program)
+        restored = ProgramDatabase(self.config)
+        self.assertEqual(expected, [2])
+        self.assertEqual(
+            restored._calculate_feature_coords(restored.programs[self.program.id]), expected
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()