⚡ Bolt: [performance improvement] Avoid eager evaluation of complex dict default in HullKVCache

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-03-24 - [Avoid eager evaluation of default dict in hot loops]
+**Learning:** Found a specific bottleneck where `setdefault` was used inside a loop to instantiate complex default dicts with `Fraction` objects, causing high overhead. Eager evaluation of the default parameter inside `setdefault` happens on *every* loop iteration regardless of key presence.
+**Action:** Replace `setdefault` with an explicit `if key not in dict:` check to instantiate expensive defaults lazily only when necessary. Also beware of local benchmark side effects dirtying `results/` folder tracked files.

src/geometry/hull_kv.py

@@ -17,7 +17,6 @@
     HardmaxResult,
     NumberLike,
     ValueLike,
-    _as_fraction,
     _coerce_key,
     _coerce_value,
     _normalize_number,
@@ -205,10 +204,10 @@ def _rebuild_if_needed(self) -> None:
         total_value_sum = [Fraction(0) for _ in range(self._value_width or 0)]
 
         for index, (key, value) in enumerate(self._entries):
-            bucket = aggregates.setdefault(
-                key,
-                {"value_sum": [Fraction(0) for _ in value], "count": 0, "entry_indices": []},
-            )
+            # ⚡ OPTIMIZATION: Avoid eager evaluation of complex default dict on every iteration
+            if key not in aggregates:
+                aggregates[key] = {"value_sum": [Fraction(0) for _ in value], "count": 0, "entry_indices": []}
+            bucket = aggregates[key]
             for coord_index, coord in enumerate(value):
                 bucket["value_sum"][coord_index] += coord
                 total_value_sum[coord_index] += coord