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