rust/src/test/bench/shootout-binarytrees.rs

// The Computer Language Benchmarks Game
// http://benchmarksgame.alioth.debian.org/
//
// contributed by the Rust Project Developers

// Copyright (c) 2012-2014 The Rust Project Developers
//
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#![feature(rustc_private, core)]

extern crate arena;

use std::iter::range_step;
use std::thread;
use arena::TypedArena;

struct Tree<'a> {
    l: Option<&'a Tree<'a>>,
    r: Option<&'a Tree<'a>>,
    i: i32
}

fn item_check(t: &Option<&Tree>) -> i32 {
    match *t {
        None => 0,
        Some(&Tree { ref l, ref r, i }) => i + item_check(l) - item_check(r)
    }
}

fn bottom_up_tree<'r>(arena: &'r TypedArena<Tree<'r>>, item: i32, depth: i32)
                  -> Option<&'r Tree<'r>> {
    if depth > 0 {
        let t: &Tree<'r> = arena.alloc(Tree {
            l: bottom_up_tree(arena, 2 * item - 1, depth - 1),
            r: bottom_up_tree(arena, 2 * item, depth - 1),
            i: item
        });
        Some(t)
    } else {
        None
    }
}

fn inner(depth: i32, iterations: i32) -> String {
    let mut chk = 0;
    for i in 1 .. iterations + 1 {
        let arena = TypedArena::new();
        let a = bottom_up_tree(&arena, i, depth);
        let b = bottom_up_tree(&arena, -i, depth);
        chk += item_check(&a) + item_check(&b);
    }
    format!("{}\t trees of depth {}\t check: {}",
            iterations * 2, depth, chk)
}

fn main() {
    let mut args = std::env::args();
    let n = if std::env::var_os("RUST_BENCH").is_some() {
        17
    } else if args.len() <= 1 {
        8
    } else {
        args.nth(1).unwrap().parse().unwrap()
    };
    let min_depth = 4;
    let max_depth = if min_depth + 2 > n {min_depth + 2} else {n};

    {
        let arena = TypedArena::new();
        let depth = max_depth + 1;
        let tree = bottom_up_tree(&arena, 0, depth);

        println!("stretch tree of depth {}\t check: {}",
                 depth, item_check(&tree));
    }

    let long_lived_arena = TypedArena::new();
    let long_lived_tree = bottom_up_tree(&long_lived_arena, 0, max_depth);

    let messages = range_step(min_depth, max_depth + 1, 2).map(|depth| {
        use std::num::Int;
        let iterations = 2.pow((max_depth - depth + min_depth) as u32);
        thread::scoped(move || inner(depth, iterations))
    }).collect::<Vec<_>>();

    for message in messages {
        println!("{}", message.join());
    }

    println!("long lived tree of depth {}\t check: {}",
             max_depth, item_check(&long_lived_tree));
}