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⚡ Bolt: [avoid dict.setdefault eager evaluation in hot loop] #15

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⚡ Bolt: [avoid dict.setdefault eager evaluation in hot loop] #15

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
## 2024-05-15 - [Avoid dict.setdefault in hot loops with complex defaults]
**Learning:** `dict.setdefault(key, complex_default)` eagerly evaluates the default value even when the key exists. In hot loops, especially with dictionary/list comprehensions or complex object creation as the default value, this introduces measurable overhead.
**Action:** Replace `dict.setdefault(key, complex_default)` with an explicit `if key not in dict: dict[key] = complex_default` followed by `bucket = dict[key]` in performance-critical loops.
9 changes: 4 additions & 5 deletions src/geometry/hull_kv.py
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,6 @@
HardmaxResult,
NumberLike,
ValueLike,
_as_fraction,
_coerce_key,
_coerce_value,
_normalize_number,
Expand Down Expand Up @@ -204,11 +203,11 @@ def _rebuild_if_needed(self) -> None:
aggregates: dict[tuple[Fraction, Fraction], dict[str, object]] = {}
total_value_sum = [Fraction(0) for _ in range(self._value_width or 0)]

# ⚡ Bolt Optimization: Avoid eager evaluation of complex defaults in hot loop
for index, (key, value) in enumerate(self._entries):
bucket = aggregates.setdefault(
key,
{"value_sum": [Fraction(0) for _ in value], "count": 0, "entry_indices": []},
)
if key not in aggregates:
aggregates[key] = {"value_sum": [Fraction(0) for _ in value], "count": 0, "entry_indices": []}
bucket = aggregates[key]
Comment on lines +206 to +210

Copilot AI Apr 9, 2026

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This does two dict lookups per iteration (key not in aggregates then aggregates[key]). Since this is a hot loop, consider a single-lookup approach (e.g., try/except KeyError or bucket = aggregates.get(key) with initialization) to avoid the extra hash-table probe when the key already exists.

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for coord_index, coord in enumerate(value):
bucket["value_sum"][coord_index] += coord
total_value_sum[coord_index] += coord
Expand Down