79 lines
1.3 KiB
Go
79 lines
1.3 KiB
Go
/*
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https://benchmarksgame-team.pages.debian.net/benchmarksgame/performance/spectralnorm.html
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Added: Pradeep Verghese
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Benchmarks:
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Used v -prod spectral.v
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Command: time ./spectral 5500
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Output: 1.274224153
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Time: 11.67s user 0.02s system 99% cpu 11.721 total
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*/
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module main
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import math
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import os
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fn evala(i, j int) int {
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return ((i+j)*(i+j+1)/2 + i + 1)
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}
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fn (v mut []f64) times(u []f64) {
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for i := 0; i < v.len; i++ {
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mut a := f64(0)
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for j :=0; j< u.len; j++ {
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a += u[j] /f64(evala(i,j))
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}
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v[i] = a
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}
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}
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fn (v mut []f64) times_trans(u []f64) {
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for i := 0; i< v.len; i++ {
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mut a := f64(0)
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for j :=0; j< u.len; j++ {
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a += u[j] / f64(evala(j,i))
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}
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v[i] = a
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}
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}
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fn (v mut []f64) a_times_transp(u []f64) {
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mut x := [f64(0); u.len]
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x.times(u)
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v.times_trans(x)
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}
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fn main() {
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args := os.args
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mut n := int(0)
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if args.len == 2 {
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n = args[1].int()
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}
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else {
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n = 0
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}
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mut u := [f64(1.0);n]
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mut v := [f64(1.0);n]
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for i := 0; i< 10; i++ {
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v.a_times_transp(u)
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u.a_times_transp(v)
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}
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mut vbv := f64(0)
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mut vv := f64(0)
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for i :=0; i< n; i++ {
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vbv += u[i] * v[i]
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vv += v[i] * v[i]
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}
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ans := math.sqrt(vbv/vv)
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println('${ans:0.9f}')
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}
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