[Autoloop: perf-comparison] Iteration 412: readParquet/toParquet benchmark

Add Parquet round-trip benchmark (10k rows × 3 cols, 20 iters).
Covers readParquet and toParquet vs pandas read_parquet/to_parquet.

Run: https://github.com/githubnext/tsb/actions/runs/29746441004

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

benchmarks/pandas/bench_readParquet.py

@@ -0,0 +1,42 @@
+"""
+Benchmark: read_parquet / to_parquet — Parquet round-trip on 10k rows
+"""
+import json
+import time
+import io
+import pandas as pd
+import numpy as np
+
+ROWS = 10_000
+WARMUP = 3
+ITERATIONS = 20
+
+rng = np.random.default_rng(42)
+df = pd.DataFrame({
+    "id": np.arange(ROWS, dtype=np.int64),
+    "value": np.arange(ROWS, dtype=np.float64) * 1.1,
+    "label": [f"cat_{i % 50}" for i in range(ROWS)],
+})
+
+# Warm up
+for _ in range(WARMUP):
+    buf = io.BytesIO()
+    df.to_parquet(buf)
+    buf.seek(0)
+    pd.read_parquet(buf)
+
+# Measure round-trip
+start = time.perf_counter()
+for _ in range(ITERATIONS):
+    buf = io.BytesIO()
+    df.to_parquet(buf)
+    buf.seek(0)
+    pd.read_parquet(buf)
+total = (time.perf_counter() - start) * 1000
+
+print(json.dumps({
+    "function": "readParquet",
+    "mean_ms": total / ITERATIONS,
+    "iterations": ITERATIONS,
+    "total_ms": total,
+}))

benchmarks/tsb/bench_readParquet.ts

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+/**
+ * Benchmark: readParquet / toParquet — Parquet round-trip on 10k rows
+ */
+import { DataFrame, toParquet, readParquet } from "../../src/index.js";
+
+const ROWS = 10_000;
+const WARMUP = 3;
+const ITERATIONS = 20;
+
+// Build a DataFrame with int, float, and string columns
+const ids = Array.from({ length: ROWS }, (_, i) => i);
+const values = Array.from({ length: ROWS }, (_, i) => i * 1.1);
+const labels = Array.from({ length: ROWS }, (_, i) => `cat_${i % 50}`);
+
+const df = new DataFrame({ id: ids, value: values, label: labels });
+
+// Warm up
+for (let i = 0; i < WARMUP; i++) {
+  const buf = toParquet(df);
+  readParquet(buf);
+}
+
+// Measure round-trip
+const start = performance.now();
+for (let i = 0; i < ITERATIONS; i++) {
+  const buf = toParquet(df);
+  readParquet(buf);
+}
+const total = performance.now() - start;
+
+console.log(
+  JSON.stringify({
+    function: "readParquet",
+    mean_ms: total / ITERATIONS,
+    iterations: ITERATIONS,
+    total_ms: total,
+  }),
+);