binary-trees Rust program

// The Computer Language Benchmarks Game
// https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
//
// contributed by the Rust Project Developers
// contributed by TeXitoi
// *reset*

extern crate typed_arena;

use std::thread;
use typed_arena::Arena;

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

fn item_check(t: &Option<&Tree>) -> i32 {
    match *t {
        None => 0,
        Some(&Tree { ref l, ref r }) => 1 + item_check(l) + item_check(r)
    }
}

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

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

fn main() {
    let n = std::env::args_os().nth(1)
        .and_then(|s| s.into_string().ok())
        .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..max_depth + 1).filter(|&d| d % 2 == 0).map(|depth| {
        let iterations = 1 << ((max_depth - depth + min_depth) as u32);
        thread::spawn(move || inner(depth, iterations))
    }).collect::<Vec<_>>();

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

    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 20:05:41 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_run
warning: unused variable: `i`
  --> binarytrees.rs:40:9
   |
40 |     for i in 1 .. iterations + 1 {
   |         ^ help: if this is intentional, prefix it with an underscore: `_i`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: 1 warning emitted

rm binarytrees.rs

14.68s to complete and log all make actions

COMMAND LINE:
./binarytrees.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