69 lines
1.2 KiB
V
69 lines
1.2 KiB
V
/*
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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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import strconv
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fn evala(i int, 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 times(mut v []f64, u []f64) {
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for i in 0 .. v.len {
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mut a := f64(0)
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for j in 0 .. u.len {
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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 times_trans(mut v []f64, u []f64) {
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for i in 0 .. v.len {
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mut a := f64(0)
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for j in 0 .. u.len {
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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 a_times_transp(mut v []f64, u []f64) {
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mut x := []f64{len: u.len, init: 0}
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times(mut x, u)
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times_trans(mut v, x)
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}
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fn main() {
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mut n := 0
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if os.args.len == 2 {
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n = strconv.atoi(os.args[1]) or { 0 }
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} else {
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n = 0
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}
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mut u := []f64{len: n, init: 1}
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mut v := []f64{len: n, init: 1}
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for _ in 0 .. 10 {
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a_times_transp(mut v, u)
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a_times_transp(mut u, 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 in 0 .. n {
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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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