source code
/* The Computer Language Benchmarks Game
* https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
*
* contributed by K P anonymous
* corrected by Isaac Gouy
*/
package main
import (
"flag"
"fmt"
"math"
"runtime"
"strconv"
)
var n = 0 // var n = flag.Int("n", 2000, "count")
var nCPU = 4 // var nCPU = flag.Int("ncpu", 4, "number of cpus")
type Vec []float64
func (v Vec) Times(ii, n int, u Vec, c chan int) {
ul := len(u)
for i := ii; i < n; i++ {
var vi float64
for j := 0; j < ul; j++ {
vi += u[j] / float64(A(i, j))
}
v[i] = vi
}
c <- 1
}
func (v Vec) TimesTransp(ii, n int, u Vec, c chan int) {
ul := len(u)
for i := ii; i < n; i++ {
var vi float64
for j := 0; j < ul; j++ {
vi += u[j] / float64(A(j, i))
}
v[i] = vi
}
c <- 1
}
func wait(c chan int) {
for i := 0; i < nCPU; i++ {
<-c
}
}
func (v Vec) ATimesTransp(u Vec) {
x := make(Vec, len(u))
c := make(chan int, nCPU)
for i := 0; i < nCPU; i++ {
go x.Times(i*len(v)/nCPU, (i+1)*len(v)/nCPU, u, c)
}
wait(c)
for i := 0; i < nCPU; i++ {
go v.TimesTransp(i*len(v)/nCPU, (i+1)*len(v)/nCPU, x, c)
}
wait(c)
}
func A(i, j int) int {
return ((i+j)*(i+j+1)/2 + i + 1)
}
func main() {
flag.Parse()
if flag.NArg() > 0 {
n, _ = strconv.Atoi(flag.Arg(0))
}
runtime.GOMAXPROCS(nCPU)
u := make(Vec, n)
for i := range u {
u[i] = 1
}
v := make(Vec, n)
for i := 0; i < 10; i++ {
v.ATimesTransp(u)
u.ATimesTransp(v)
}
var vBv, vv float64
for i, vi := range v {
vBv += u[i] * vi
vv += vi * vi
}
fmt.Printf("%0.9f\n", math.Sqrt(vBv/vv))
}
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
go version go1.22.0 linux/amd64
GOAMD64=v2
Sat, 02 Mar 2024 00:02:02 GMT
MAKE:
/opt/src/go1.22.0/go/bin/go build -o spectralnorm.go-4.go_run spectralnorm.go-4.go
4.98s to complete and log all make actions
COMMAND LINE:
./spectralnorm.go-4.go_run 5500
PROGRAM OUTPUT:
1.274224153