src/test/bench/shootout-spectralnorm.rs

   1 // The Computer Language Benchmarks Game
   2 // http://benchmarksgame.alioth.debian.org/
   3 //
   4 // contributed by the Rust Project Developers
   5
   6 // Copyright (c) 2012-2014 The Rust Project Developers
   7 //
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  11 // modification, are permitted provided that the following conditions
  12 // are met:
  13 //
  14 // - Redistributions of source code must retain the above copyright
  15 //   notice, this list of conditions and the following disclaimer.
  16 //
  17 // - Redistributions in binary form must reproduce the above copyright
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  19 //   the documentation and/or other materials provided with the
  20 //   distribution.
  21 //
  22 // - Neither the name of "The Computer Language Benchmarks Game" nor
  23 //   the name of "The Computer Language Shootout Benchmarks" nor the
  24 //   names of its contributors may be used to endorse or promote
  25 //   products derived from this software without specific prior
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  27 //
  28 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  29 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  40
  41 // no-pretty-expanded FIXME #15189
  42
  43 #![allow(non_snake_case)]
  44 #![feature(unboxed_closures, iter_arith, core_simd, scoped)]
  45
  46 use std::thread;
  47 use std::env;
  48 use std::simd::f64x2;
  49
  50 fn main() {
  51     let mut args = env::args();
  52     let answer = spectralnorm(if env::var_os("RUST_BENCH").is_some() {
  53         5500
  54     } else if args.len() < 2 {
  55         2000
  56     } else {
  57         args.nth(1).unwrap().parse().unwrap()
  58     });
  59     println!("{:.9}", answer);
  60 }
  61
  62 fn spectralnorm(n: usize) -> f64 {
  63     assert!(n % 2 == 0, "only even lengths are accepted");
  64     let mut u = vec![1.0; n];
  65     let mut v = u.clone();
  66     let mut tmp = v.clone();
  67     for _ in 0..10 {
  68         mult_AtAv(&u, &mut v, &mut tmp);
  69         mult_AtAv(&v, &mut u, &mut tmp);
  70     }
  71     (dot(&u, &v) / dot(&v, &v)).sqrt()
  72 }
  73
  74 fn mult_AtAv(v: &[f64], out: &mut [f64], tmp: &mut [f64]) {
  75     mult_Av(v, tmp);
  76     mult_Atv(tmp, out);
  77 }
  78
  79 fn mult_Av(v: &[f64], out: &mut [f64]) {
  80     parallel(out, |start, out| mult(v, out, start, |i, j| A(i, j)));
  81 }
  82
  83 fn mult_Atv(v: &[f64], out: &mut [f64]) {
  84     parallel(out, |start, out| mult(v, out, start, |i, j| A(j, i)));
  85 }
  86
  87 fn mult<F>(v: &[f64], out: &mut [f64], start: usize, a: F)
  88            where F: Fn(usize, usize) -> f64 {
  89     for (i, slot) in out.iter_mut().enumerate().map(|(i, s)| (i + start, s)) {
  90         let mut sum = f64x2(0.0, 0.0);
  91         for (j, chunk) in v.chunks(2).enumerate().map(|(j, s)| (2 * j, s)) {
  92             let top = f64x2(chunk[0], chunk[1]);
  93             let bot = f64x2(a(i, j), a(i, j + 1));
  94             sum += top / bot;
  95         }
  96         let f64x2(a, b) = sum;
  97         *slot = a + b;
  98     }
  99 }
 100
 101 fn A(i: usize, j: usize) -> f64 {
 102     ((i + j) * (i + j + 1) / 2 + i + 1) as f64
 103 }
 104
 105 fn dot(v: &[f64], u: &[f64]) -> f64 {
 106     v.iter().zip(u).map(|(a, b)| *a * *b).sum()
 107 }
 108
 109
 110 // Executes a closure in parallel over the given mutable slice. The closure `f`
 111 // is run in parallel and yielded the starting index within `v` as well as a
 112 // sub-slice of `v`.
 113 fn parallel<'a,T, F>(v: &mut [T], ref f: F)
 114                   where T: Send + Sync + 'a,
 115                         F: Fn(usize, &mut [T]) + Sync + 'a {
 116     // FIXME: pick a more appropriate parallel factor
 117     let parallelism = 4;
 118     let size = v.len() / parallelism + 1;
 119     v.chunks_mut(size).enumerate().map(|(i, chunk)| {
 120         thread::scoped(move|| {
 121             f(i * size, chunk)
 122         })
 123     }).collect::<Vec<_>>();
 124 }