binary-trees Rust #4 program

// The Computer Language Benchmarks Game
// http://benchmarksgame.alioth.debian.org/
//
// contributed by the Rust Project Developers
// contributed by TeXitoi
// contributed by Cristi Cobzarenco
// contributed by Matt Brubeck
// modified by Tom Kaitchuck
// modified by Volodymyr M. Lisivka

extern crate rayon;
extern crate toolshed;

use toolshed::Arena;
use rayon::prelude::*;

#[derive(Debug, PartialEq, Clone, Copy)]
struct Tree<'a> {
    left: Option<&'a Tree<'a>>,
    right: Option<&'a Tree<'a>>,
}

fn item_check(tree: &Tree) -> i32 {
    if let (Some(left), Some(right)) = (tree.left, tree.right) {
        1 + item_check(right) + item_check(left)
    } else {
        1
    }
}

fn bottom_up_tree<'r>(arena: &'r Arena, depth: i32)
                  -> &'r Tree<'r> {
    let tree = arena.alloc(Tree { left: None, right: None });
    if depth > 0 {
        tree.right = Some(bottom_up_tree(arena, depth - 1));
        tree.left = Some(bottom_up_tree(arena, depth - 1));
    }
    tree
}

fn inner(depth: i32, iterations: i32) -> String {
    let chk: i32 = (0 .. iterations).into_par_iter().map(|_| {
        let arena = Arena::new();
        let a = bottom_up_tree(&arena, depth);
        item_check(a)
    }).sum();
    format!("{}\t trees of depth {}\t check: {}", iterations, depth, chk)
}

fn main() {
    let n = std::env::args().nth(1)
        .and_then(|n| n.parse().ok())
        .unwrap_or(10);
    let min_depth = 4;
    let max_depth = if min_depth + 2 > n { min_depth + 2 } else { n };

    {
        let arena = Arena::new();
        let depth = max_depth + 1;
        let tree = bottom_up_tree(&arena, depth);
        println!("stretch tree of depth {}\t check: {}", depth, item_check(tree));
    }

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

    let messages = (min_depth/2..max_depth/2 + 1).into_par_iter().map(|half_depth| {
            let depth = half_depth * 2;
            let iterations = 1 << ((max_depth - depth + min_depth) as u32);
            inner(depth, iterations)
        }).collect::<Vec<_>>();

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

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

NOTES:
64-bit Ubuntu quad core
rustc 1.44.0 (49cae5576 2020-06-01)
LLVM version: 9.0


Fri, 05 Jun 2020 20:07:24 GMT

MAKE:
/opt/src/rust-1.44.0/bin/rustc -C opt-level=3 -C target-cpu=core2 -C lto -C codegen-units=1 -L /opt/src/rust-libs binarytrees.rs -o binarytrees.rust-4.rust_run

17.96s to complete and log all make actions

COMMAND LINE:
./binarytrees.rust-4.rust_run 21

PROGRAM OUTPUT:
stretch tree of depth 22	 check: 8388607
2097152	 trees of depth 4	 check: 65011712
524288	 trees of depth 6	 check: 66584576
131072	 trees of depth 8	 check: 66977792
32768	 trees of depth 10	 check: 67076096
8192	 trees of depth 12	 check: 67100672
2048	 trees of depth 14	 check: 67106816
512	 trees of depth 16	 check: 67108352
128	 trees of depth 18	 check: 67108736
32	 trees of depth 20	 check: 67108832
long lived tree of depth 21	 check: 4194303