collatz.rs

extern crate rayon;
use rayon::prelude::*;
use std::sync::atomic::{AtomicU8, Ordering};

fn main() {
  let pos = AtomicU8::new(0);

  (2..(u32::MAX as u64)).into_par_iter().for_each(|num| {
    let mut inter = num;
    while inter >= num {
      if inter % 2 == 0 {
        inter = inter / 2;
      } else {
        inter = (3 * inter + 1) / 2;
      }
    }

    if num % (u32::MAX as u64 / 100) == 0 {
      let val = pos.fetch_add(1, Ordering::SeqCst);
      println!("Checked up to {}%", val+1);
    }
  });
}