gcc/testsuite/go.test/test/bench/spectral-norm.go

   1 /*
   2 Redistribution and use in source and binary forms, with or without
   3 modification, are permitted provided that the following conditions are met:
   4
   5     * Redistributions of source code must retain the above copyright
   6     notice, this list of conditions and the following disclaimer.
   7
   8     * Redistributions in binary form must reproduce the above copyright
   9     notice, this list of conditions and the following disclaimer in the
  10     documentation and/or other materials provided with the distribution.
  11
  12     * Neither the name of "The Computer Language Benchmarks Game" nor the
  13     name of "The Computer Language Shootout Benchmarks" nor the names of
  14     its contributors may be used to endorse or promote products derived
  15     from this software without specific prior written permission.
  16
  17 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  18 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20 ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  21 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  22 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  23 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  24 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  25 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  26 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  27 POSSIBILITY OF SUCH DAMAGE.
  28 */
  29
  30 /* The Computer Language Benchmarks Game
  31  * http://shootout.alioth.debian.org/
  32  *
  33  * contributed by The Go Authors.
  34  * Based on spectral-norm.c by Sebastien Loisel
  35  */
  36
  37 package main
  38
  39 import (
  40         "flag"
  41         "fmt"
  42         "math"
  43 )
  44
  45 var n = flag.Int("n", 2000, "count")
  46
  47 func evalA(i, j int) float64 { return 1 / float64(((i+j)*(i+j+1)/2 + i + 1)) }
  48
  49 type Vec []float64
  50
  51 func (v Vec) Times(u Vec) {
  52         for i := 0; i < len(v); i++ {
  53                 v[i] = 0
  54                 for j := 0; j < len(u); j++ {
  55                         v[i] += evalA(i, j) * u[j]
  56                 }
  57         }
  58 }
  59
  60 func (v Vec) TimesTransp(u Vec) {
  61         for i := 0; i < len(v); i++ {
  62                 v[i] = 0
  63                 for j := 0; j < len(u); j++ {
  64                         v[i] += evalA(j, i) * u[j]
  65                 }
  66         }
  67 }
  68
  69 func (v Vec) ATimesTransp(u Vec) {
  70         x := make(Vec, len(u))
  71         x.Times(u)
  72         v.TimesTransp(x)
  73 }
  74
  75 func main() {
  76         flag.Parse()
  77         N := *n
  78         u := make(Vec, N)
  79         for i := 0; i < N; i++ {
  80                 u[i] = 1
  81         }
  82         v := make(Vec, N)
  83         for i := 0; i < 10; i++ {
  84                 v.ATimesTransp(u)
  85                 u.ATimesTransp(v)
  86         }
  87         var vBv, vv float64
  88         for i := 0; i < N; i++ {
  89                 vBv += u[i] * v[i]
  90                 vv += v[i] * v[i]
  91         }
  92         fmt.Printf("%0.9f\n", math.Sqrt(vBv/vv))
  93 }