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tensor/io/csv_bench_test.go
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2026-09-03 10:00:00 +02:00
// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT
package io
// The A/B benchmark for the CSV read path: the legacy encoding/csv
// reader and the hand-rolled tokenizer side by side, in one process.
// The two sub-benchmarks alternate within every -count round, so both
// see the same machine, and the decision reads the medians with 1 to 2
// percent treated as noise.
import (
"bytes"
"io"
"testing"
"sourcedock.dev/petrbalvin/tensor/internal/core"
)
// The A/B table: a hundred thousand rows of sixteen float64 values, in
// the text shape SaveCSV emits, sized so the per-value work dominates
// everything else.
const (
benchCSVABRows = 100000
benchCSVABCols = 16
)
// benchCSVABData renders the A/B table as CSV bytes, once, before the
// measured loops.
func benchCSVABData(b *testing.B) []byte {
b.Helper()
var buf bytes.Buffer
if err := SaveCSVWriter(&buf, benchFloats(benchCSVABRows, benchCSVABCols)); err != nil {
b.Fatal(err)
}
return buf.Bytes()
}
// BenchmarkLoadCSVReader races the two readers over the same table.
func BenchmarkLoadCSVReader(b *testing.B) {
data := benchCSVABData(b)
impls := []struct {
name string
load func(io.Reader, bool) (*core.Array, error)
}{
{"old", loadCSVReaderLegacy},
{"new", LoadCSVReader},
}
for _, impl := range impls {
b.Run(impl.name, func(b *testing.B) {
r := bytes.NewReader(data)
b.ReportAllocs()
for b.Loop() {
r.Reset(data)
a, err := impl.load(r, false)
if err != nil {
b.Fatal(err)
}
if a.Shape()[0] != benchCSVABRows || a.Shape()[1] != benchCSVABCols {
b.Fatalf("array came back with shape %v", a.Shape())
}
}
})
}
}