Improve error logging and handle stale feature map references

Use logger.exception for better error tracebacks in controller.py. In database.py, ensure feature map entries are updated if the referenced program no longer exists, preventing stale references and improving robustness.

Author: codelion

openevolve/controller.py

@@ -405,8 +405,7 @@ async def run(
                             break
 
             except Exception as e:
-                logger.error(f"Error in iteration {i+1}: {str(e)}")
-                traceback.print_exc()
+                logger.exception(f"Error in iteration {i+1}: {str(e)}")
                 continue
 
         # Get the best program using our tracking mechanism

openevolve/database.py

@@ -161,9 +161,20 @@ def add(
 
         # Add to feature map (replacing existing if better)
         feature_key = self._feature_coords_to_key(feature_coords)
-        if feature_key not in self.feature_map or self._is_better(
-            program, self.programs[self.feature_map[feature_key]]
-        ):
+        should_replace = feature_key not in self.feature_map
+        
+        if not should_replace:
+            # Check if the existing program still exists before comparing
+            existing_program_id = self.feature_map[feature_key]
+            if existing_program_id not in self.programs:
+                # Stale reference, replace it
+                should_replace = True
+                logger.debug(f"Replacing stale program reference {existing_program_id} in feature map")
+            else:
+                # Program exists, compare fitness
+                should_replace = self._is_better(program, self.programs[existing_program_id])
+        
+        if should_replace:
             self.feature_map[feature_key] = program.id
 
         # Add to specific island (not random!)