⚡ Bolt: [performance improvement] Replace iterrows with to_dict('records')

.jules/bolt.md

@@ -8,3 +8,6 @@
 ## 2024-03-29 - ASE Custom JSON encoding vs standard JSON
 **Learning:** ASE's custom JSON encoder (`ase.io.jsonio.encode`) will generate dicts with special keys like `__ndarray__` or `__complex__` (e.g. `{"__ndarray__": [[5], "int64", ...]}`). When optimizing JSON deserialization using faster alternatives like `orjson`, it's critical to realize that a normal `json.loads` or `orjson.loads` will deserialize this into a Python dictionary, while ASE's custom `decode` will properly reconstruct the underlying numpy array. Bypassing ASE's decoder without checking for these keys leads to downstream type errors (e.g. `KeyError: '__ndarray__'`).
 **Action:** When replacing or wrapping ASE's jsonio with `orjson`, always fall back to ASE's `decode` if the payload string contains `__ndarray__` or `__complex__` markers, to ensure custom objects are correctly reconstructed.
+## 2024-05-19 - Replacing iterrows with to_dict('records')
+**Learning:** In data handling files like `verify_processed_omol25.py`, iterating over large Pandas DataFrames using `df.iterrows()` is an anti-pattern that creates significant bottlenecks because it instantiates a Pandas Series object for every single row. A highly performant alternative is to convert the DataFrame to a list of dicts using `df.to_dict('records')` first.
+**Action:** When iterating over a pandas DataFrame, especially large ones, use `df.to_dict('records')` instead of `df.iterrows()`. Remember to update downstream method calls on the row object (e.g., replacing `row.to_dict()` with `dict(row)` or just `row`), as the row is now a native Python dictionary instead of a Pandas Series.

src/lavello_mlips/verify_processed_omol25.py

@@ -77,8 +77,12 @@ def main() -> None:
         )
 
     logger.info(f"Loaded {len(df)} records from Parquet.")
-    parquet_by_sha = {row["geom_sha1"]: row for _, row in df.iterrows()}
-    parquet_by_argone_rel = {row["argonne_rel"]: row for _, row in df.iterrows()}
+    # Performance Optimization: Convert DataFrame to a list of dicts.
+    # Iterating over native Python dicts is ~10x faster than using df.iterrows()
+    # because it avoids the overhead of instantiating a Pandas Series for every row.
+    records = df.to_dict("records")
+    parquet_by_sha = {row["geom_sha1"]: row for row in records}
+    parquet_by_argone_rel = {row["argonne_rel"]: row for row in records}
     logger.info(f"Loading ExtXYZ file from {args.extxyz} (this may take a moment)...")
     all_atoms = read(str(args.extxyz), index=":")
     if not isinstance(all_atoms, list):
@@ -108,7 +112,9 @@ def get_dump_entry(at):
             info = dict(at.info)
             rel = info.get("argonne_rel")
             pq_row = parquet_by_argone_rel.get(rel)
-            pq_data = pq_row.to_dict() if pq_row is not None else None
+            # Performance Optimization: pq_row is now a native dict instead of a Pandas Series,
+            # so we use dict(pq_row) instead of pq_row.to_dict().
+            pq_data = dict(pq_row) if pq_row is not None else None
             return {"xyz": info, "parquet": pq_data}
 
         duplicates = {