Commit 72b09bd7 authored by Dmitriy Vyukov's avatar Dmitriy Vyukov

runtime: add matrix multiplication benchmark

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7431047
parent bd889907
......@@ -5,6 +5,7 @@
package runtime_test
import (
"math"
"runtime"
"sync/atomic"
"testing"
......@@ -225,3 +226,67 @@ func benchmarkCreateGoroutines(b *testing.B, procs int) {
<-c
}
}
type Matrix [][]float64
func BenchmarkMatmult(b *testing.B) {
b.StopTimer()
// matmult is O(N**3) but testing expects O(b.N),
// so we need to take cube root of b.N
n := int(math.Cbrt(float64(b.N))) + 1
A := makeMatrix(n)
B := makeMatrix(n)
C := makeMatrix(n)
b.StartTimer()
matmult(nil, A, B, C, 0, n, 0, n, 0, n, 8)
}
func makeMatrix(n int) Matrix {
m := make(Matrix, n)
for i := 0; i < n; i++ {
m[i] = make([]float64, n)
for j := 0; j < n; j++ {
m[i][j] = float64(i*n + j)
}
}
return m
}
func matmult(done chan<- struct{}, A, B, C Matrix, i0, i1, j0, j1, k0, k1, threshold int) {
di := i1 - i0
dj := j1 - j0
dk := k1 - k0
if di >= dj && di >= dk && di >= threshold {
// divide in two by y axis
mi := i0 + di/2
done1 := make(chan struct{}, 1)
go matmult(done1, A, B, C, i0, mi, j0, j1, k0, k1, threshold)
matmult(nil, A, B, C, mi, i1, j0, j1, k0, k1, threshold)
<-done1
} else if dj >= dk && dj >= threshold {
// divide in two by x axis
mj := j0 + dj/2
done1 := make(chan struct{}, 1)
go matmult(done1, A, B, C, i0, i1, j0, mj, k0, k1, threshold)
matmult(nil, A, B, C, i0, i1, mj, j1, k0, k1, threshold)
<-done1
} else if dk >= threshold {
// divide in two by "k" axis
// deliberately not parallel because of data races
mk := k0 + dk/2
matmult(nil, A, B, C, i0, i1, j0, j1, k0, mk, threshold)
matmult(nil, A, B, C, i0, i1, j0, j1, mk, k1, threshold)
} else {
// the matrices are small enough, compute directly
for i := i0; i < i1; i++ {
for j := j0; j < j1; j++ {
for k := k0; k < k1; k++ {
C[i][j] += A[i][k] * B[k][j]
}
}
}
}
if done != nil {
done <- struct{}{}
}
}
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