rust/src/test/bench/shootout-spectralnorm.rs
Graydon Hoare 6f5853f5a1 Libc/os/run/rand/io reorganization. Close #1373. Close #1638.
- Move io, run and rand to core.
 - Remove incorrect ctypes module (use libc).
 - Remove os-specific modules for os and fs.
 - Split fs between core::path and core::os.
2012-03-12 20:08:29 -07:00

71 lines
1.4 KiB
Rust

// Based on spectalnorm.gcc by Sebastien Loisel
use std;
fn eval_A(i: uint, j: uint) -> float {
1.0/(((i+j)*(i+j+1u)/2u+i+1u) as float)
}
fn eval_A_times_u(u: [const float], Au: [mutable float]) {
let N = vec::len(u);
let i = 0u;
while i < N {
Au[i] = 0.0;
let j = 0u;
while j < N {
Au[i] += eval_A(i, j) * u[j];
j += 1u;
}
i += 1u;
}
}
fn eval_At_times_u(u: [const float], Au: [mutable float]) {
let N = vec::len(u);
let i = 0u;
while i < N {
Au[i] = 0.0;
let j = 0u;
while j < N {
Au[i] += eval_A(j, i) * u[j];
j += 1u;
}
i += 1u;
}
}
fn eval_AtA_times_u(u: [const float], AtAu: [mutable float]) {
let v = vec::to_mut(vec::init_elt(vec::len(u), 0.0));
eval_A_times_u(u, v);
eval_At_times_u(v, AtAu);
}
fn main(args: [str]) {
let N = if vec::len(args) == 2u {
option::get(uint::from_str(args[1]))
} else {
1000u
};
let u = vec::to_mut(vec::init_elt(N, 1.0));
let v = vec::to_mut(vec::init_elt(N, 0.0));
let i = 0u;
while i < 10u {
eval_AtA_times_u(u, v);
eval_AtA_times_u(v, u);
i += 1u;
}
let vBv = 0.0;
let vv = 0.0;
let i = 0u;
while i < N {
vBv += u[i] * v[i];
vv += v[i] * v[i];
i += 1u;
}
io::println(#fmt("%0.9f\n", float::sqrt(vBv / vv)));
}