tensor/internal/core/bench_test.go

// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package core

import "testing"

// The matmul hot loop of inference: benchmarks keep the loop
// order honest. Compare with -bench=BenchmarkMatMul before and after any
// change to the kernels.

func BenchmarkMatMul(b *testing.B) {
	a, _ := FromFloats(make([]float64, 128*128), 128, 128)
	for i := range a.Len() {
		a.RawFloats()[i] = float64(i%7) - 3
	}
	c, _ := FromFloats(make([]float64, 128*128), 128, 128)
	for i := range c.Len() {
		c.RawFloats()[i] = float64(i%5) - 2
	}
	b.ReportAllocs()
	for b.Loop() {
		_, err := MatMul2D(a, c)
		if err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkAdd(b *testing.B) {
	x, _ := FromFloats(make([]float64, 100_000), 100_000)
	y, _ := FromFloats(make([]float64, 100_000), 100_000)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Add(x, y); err != nil {
			b.Fatal(err)
		}
	}
}

// Parallel-vs-serial comparisons: run with -bench=. to see the
// speedup the parallel kernels deliver on the host's core count. The
// serial variants pin the worker count to one.

func BenchmarkMatMulParallel(b *testing.B) {
	benchMatMulN(b, 512)
}

func BenchmarkMatMulSerial(b *testing.B) {
	SetNumCPU(1)
	defer SetNumCPU(0)
	benchMatMulN(b, 512)
}

func benchMatMulN(b *testing.B, n int) {
	a, _ := FromFloats(make([]float64, n*n), n, n)
	c, _ := FromFloats(make([]float64, n*n), n, n)
	b.ResetTimer()
	for b.Loop() {
		if _, err := MatMul2D(a, c); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkAddParallel(b *testing.B) { benchAddN(b, 1<<22) }

func BenchmarkAddSerial(b *testing.B) {
	SetNumCPU(1)
	defer SetNumCPU(0)
	benchAddN(b, 1<<22)
}

func benchAddN(b *testing.B, n int) {
	a, _ := FromFloats(make([]float64, n), n)
	c, _ := FromFloats(make([]float64, n), n)
	b.ResetTimer()
	for b.Loop() {
		if _, err := Add(a, c); err != nil {
			b.Fatal(err)
		}
	}
}

// BenchmarkMatMulFloat32 exercises the production inference dtype at
// sizes the embedding/table workloads actually see.
func BenchmarkMatMulFloat32_128(b *testing.B) { benchMatMulF32N(b, 128) }

func BenchmarkMatMulFloat32_512(b *testing.B) { benchMatMulF32N(b, 512) }

func benchMatMulF32N(b *testing.B, n int) {
	af, _ := FromFloats(make([]float64, n*n), n, n)
	bf, _ := FromFloats(make([]float64, n*n), n, n)
	a, _ := Astype(af, Float32)
	c, _ := Astype(bf, Float32)
	b.ResetTimer()
	for b.Loop() {
		if _, err := MatMul2D(a, c); err != nil {
			b.Fatal(err)
		}
	}
}

// BroadcastTo sits inside every bias add and normalisation, so its walk
// is on the training hot path. The bias-shaped case (1, C, 1, 1) to
// (N, C, H, W) is the one the run-fill rewrite targets.
func BenchmarkBroadcastToBiasNCHW(b *testing.B) {
	src, _ := FromFloats(make([]float64, 64), 1, 64, 1, 1)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := BroadcastTo(src, 8, 64, 28, 28); err != nil {
			b.Fatal(err)
		}
	}
}

// The trailing-replication case (1, C) to (N, C): the run is the whole
// channel block, the other extreme from a fully strided walk.
func BenchmarkBroadcastToBiasNC(b *testing.B) {
	src, _ := FromFloats(make([]float64, 256), 1, 256)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := BroadcastTo(src, 128, 256); err != nil {
			b.Fatal(err)
		}
	}
}

// The non-broadcast expansion (prepending leading dimensions only):
// every element is distinct, so this is the worst case for the rewrite.
func BenchmarkBroadcastToPrepend(b *testing.B) {
	src, _ := FromFloats(make([]float64, 128*256), 128, 256)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := BroadcastTo(src, 4, 128, 256); err != nil {
			b.Fatal(err)
		}
	}
}

// Reduction and vector-shaped hot paths: Dot and Min walk a single
// payload, MatVec is the 2-D×1-D product. Run with -bench before and
// after any change to reduce.go or the vector kernels in mat.go.

func benchVecF64(b *testing.B, n int) (*Array, *Array) {
	a, _ := FromFloats(make([]float64, n), n)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%11) - 5
	}
	c, _ := FromFloats(make([]float64, n), n)
	for i := range c.RawFloats() {
		c.RawFloats()[i] = float64(i%7) - 3
	}
	return a, c
}

func BenchmarkDot(b *testing.B) {
	a, c := benchVecF64(b, 1<<20)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Dot(a, c); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkMinMax(b *testing.B) {
	a, _ := benchVecF64(b, 1<<20)
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Max(a); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkMatVec(b *testing.B) {
	m, _ := FromFloats(make([]float64, 512*512), 512, 512)
	for i := range m.RawFloats() {
		m.RawFloats()[i] = float64(i%13) - 6
	}
	v, _ := FromFloats(make([]float64, 512), 512)
	for i := range v.RawFloats() {
		v.RawFloats()[i] = float64(i%7) - 3
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := MatMul2D(m, v); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkTranspose(b *testing.B) {
	a, _ := FromFloats(make([]float64, 256*256), 256, 256)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) - 4
	}
	b.ReportAllocs()
	for b.Loop() {
		Transpose(a)
	}
}

func BenchmarkRowCol(b *testing.B) {
	a, _ := FromFloats(make([]float64, 512*512), 512, 512)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) - 4
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Row(a, 7); err != nil {
			b.Fatal(err)
		}
		if _, err := Col(a, 7); err != nil {
			b.Fatal(err)
		}
	}
}

// ColTall isolates the column gather from output allocation: the tall
// shape makes the per-row strided read the dominant cost.
func BenchmarkColTall(b *testing.B) {
	a, _ := FromFloats(make([]float64, 65536*8), 65536, 8)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) - 4
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Col(a, 3); err != nil {
			b.Fatal(err)
		}
	}
}

// Along-dim reductions: Norm folds with math.Pow per element, Prod is
// the multiply twin of the axis sum. Run with -bench before and after
// any change to reduction2.go.
func BenchmarkNorm2D(b *testing.B) {
	a, _ := FromFloats(make([]float64, 512*512), 512, 512)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) - 4
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Norm(a, 2, 1, false); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkProd2D(b *testing.B) {
	a, _ := FromFloats(make([]float64, 512*512), 512, 512)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) + 1
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := Prod(a, 1, false); err != nil {
			b.Fatal(err)
		}
	}
}

// CumSum walks the prefix scan along the trailing dimension.
func BenchmarkCumSum2D(b *testing.B) {
	a, _ := FromFloats(make([]float64, 512*512), 512, 512)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%9) - 4
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := CumSum(a, 1); err != nil {
			b.Fatal(err)
		}
	}
}

// Element-wise math walks the payload through a real function; Exp and
// Sqrt are the training hot ones. Run with -bench before and after any
// change to mathfunc.go.

func benchmarkRealFunc(b *testing.B, f func(*Array) (*Array, error)) {
	a, _ := FromFloats(make([]float64, 1<<20), 1<<20)
	for i := range a.RawFloats() {
		a.RawFloats()[i] = float64(i%97) + 1
	}
	b.ReportAllocs()
	for b.Loop() {
		if _, err := f(a); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkExp(b *testing.B) { benchmarkRealFunc(b, Exp) }

func BenchmarkSqrt(b *testing.B) { benchmarkRealFunc(b, Sqrt) }

func BenchmarkProd1D(b *testing.B) {
	a, _ := FromFloats(prodFixture(1<<20), 1<<20)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		if _, err := Prod(a, 0, false); err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkNorm1D(b *testing.B) {
	a, _ := FromFloats(prodFixture(1<<20), 1<<20)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		if _, err := Norm(a, 2, 0, false); err != nil {
			b.Fatal(err)
		}
	}
}