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v/examples/spectral.v
2019-12-03 11:52:38 +03:00

79 lines
1.4 KiB
V

/*
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
fn evala(i, j int) int {
return ((i+j)*(i+j+1)/2 + i + 1)
}
fn times(v mut []f64, u []f64) {
for i := 0; i < v.len; i++ {
mut a := f64(0)
for j :=0; j< u.len; j++ {
a += u[j] /f64(evala(i,j))
}
v[i] = a
}
}
fn times_trans(v mut []f64, u []f64) {
for i := 0; i< v.len; i++ {
mut a := f64(0)
for j :=0; j< u.len; j++ {
a += u[j] / f64(evala(j,i))
}
v[i] = a
}
}
fn a_times_transp(v mut []f64, u []f64) {
mut x := [f64(0)].repeat(u.len)
times(mut x, u)
times_trans(mut v, x)
}
fn main() {
args := os.args
mut n := int(0)
if args.len == 2 {
n = args[1].int()
}
else {
n = 0
}
mut u := [f64(1.0)].repeat(n)
mut v := [f64(1.0)].repeat(n)
for i := 0; i< 10; i++ {
a_times_transp(mut v, u)
a_times_transp(mut u, v)
}
mut vbv := f64(0)
mut vv := f64(0)
for i :=0; i< n; i++ {
vbv += u[i] * v[i]
vv += v[i] * v[i]
}
ans := math.sqrt(vbv/vv)
println('${ans:0.9f}')
}