mirror of
https://github.com/golang/go
synced 2024-11-05 17:46:16 -07:00
94 lines
2.5 KiB
Go
94 lines
2.5 KiB
Go
/*
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions are met:
|
|
|
|
* Redistributions of source code must retain the above copyright
|
|
notice, this list of conditions and the following disclaimer.
|
|
|
|
* Redistributions in binary form must reproduce the above copyright
|
|
notice, this list of conditions and the following disclaimer in the
|
|
documentation and/or other materials provided with the distribution.
|
|
|
|
* Neither the name of "The Computer Language Benchmarks Game" nor the
|
|
name of "The Computer Language Shootout Benchmarks" nor the names of
|
|
its contributors may be used to endorse or promote products derived
|
|
from this software without specific prior written permission.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
|
|
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
/* The Computer Language Benchmarks Game
|
|
* http://shootout.alioth.debian.org/
|
|
*
|
|
* contributed by The Go Authors.
|
|
* Based on spectral-norm.c by Sebastien Loisel
|
|
*/
|
|
|
|
package main
|
|
|
|
import (
|
|
"flag"
|
|
"fmt"
|
|
"math"
|
|
)
|
|
|
|
var n = flag.Int("n", 2000, "count")
|
|
|
|
func evalA(i, j int) float64 { return 1 / float64(((i+j)*(i+j+1)/2 + i + 1)) }
|
|
|
|
type Vec []float64
|
|
|
|
func (v Vec) Times(u Vec) {
|
|
for i := 0; i < len(v); i++ {
|
|
v[i] = 0
|
|
for j := 0; j < len(u); j++ {
|
|
v[i] += evalA(i, j) * u[j]
|
|
}
|
|
}
|
|
}
|
|
|
|
func (v Vec) TimesTransp(u Vec) {
|
|
for i := 0; i < len(v); i++ {
|
|
v[i] = 0
|
|
for j := 0; j < len(u); j++ {
|
|
v[i] += evalA(j, i) * u[j]
|
|
}
|
|
}
|
|
}
|
|
|
|
func (v Vec) ATimesTransp(u Vec) {
|
|
x := make(Vec, len(u))
|
|
x.Times(u)
|
|
v.TimesTransp(x)
|
|
}
|
|
|
|
func main() {
|
|
flag.Parse()
|
|
N := *n
|
|
u := make(Vec, N)
|
|
for i := 0; i < N; i++ {
|
|
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 := 0; i < N; i++ {
|
|
vBv += u[i] * v[i]
|
|
vv += v[i] * v[i]
|
|
}
|
|
fmt.Printf("%0.9f\n", math.Sqrt(vBv/vv))
|
|
}
|