74 lines
1.5 KiB
Rust
74 lines
1.5 KiB
Rust
// Based on spectalnorm.gcc by Sebastien Loisel
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use std;
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fn eval_A(i: uint, j: uint) -> float {
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1.0/(((i+j)*(i+j+1u)/2u+i+1u) as float)
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}
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fn eval_A_times_u(u: [const float], Au: [mut float]) {
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let N = vec::len(u);
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let mut i = 0u;
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while i < N {
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Au[i] = 0.0;
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let mut j = 0u;
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while j < N {
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Au[i] += eval_A(i, j) * u[j];
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j += 1u;
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}
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i += 1u;
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}
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}
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fn eval_At_times_u(u: [const float], Au: [mut float]) {
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let N = vec::len(u);
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let mut i = 0u;
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while i < N {
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Au[i] = 0.0;
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let mut j = 0u;
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while j < N {
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Au[i] += eval_A(j, i) * u[j];
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j += 1u;
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}
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i += 1u;
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}
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}
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fn eval_AtA_times_u(u: [const float], AtAu: [mut float]) {
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let v = vec::to_mut(vec::from_elem(vec::len(u), 0.0));
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eval_A_times_u(u, v);
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eval_At_times_u(v, AtAu);
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}
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fn main(args: [str]) {
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let args = if os::getenv("RUST_BENCH").is_some() {
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["", "2000"]
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} else if args.len() <= 1u {
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["", "1000"]
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} else {
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args
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};
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let N = uint::from_str(args[1]).get();
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let u = vec::to_mut(vec::from_elem(N, 1.0));
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let v = vec::to_mut(vec::from_elem(N, 0.0));
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let mut i = 0u;
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while i < 10u {
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eval_AtA_times_u(u, v);
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eval_AtA_times_u(v, u);
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i += 1u;
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}
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let mut vBv = 0.0;
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let mut vv = 0.0;
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let mut i = 0u;
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while i < N {
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vBv += u[i] * v[i];
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vv += v[i] * v[i];
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i += 1u;
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}
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io::println(#fmt("%0.9f\n", float::sqrt(vBv / vv)));
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}
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