per/src/main.rs

extern crate num_bigint;
// extern crate num_traits;
extern crate num_cpus;


use num_bigint::BigUint;

use std::thread;
// use std::sync::mpsc;
use std::sync::{Arc, Barrier, RwLock};

use std::time::{Duration, Instant};


trait Stuff {
    fn factorize(&self) -> Self;
    fn test(&self) -> u8;
}

impl Stuff for BigUint {
    fn factorize(&self) -> BigUint {
        let string = self.to_str_radix(10);
        let numbers: Vec<u8> = string.chars().map(|x| x as u8 - 48).collect();
        numbers.into_iter().product::<BigUint>()
    }
    
    fn test(&self) -> u8 {
        let mut n = self.factorize();
        let mut counter = 1;
        while n.to_str_radix(10).chars().count() > 1 {
            n = n.factorize();
            counter += 1;
        }
        return counter;
    }
}


#[derive(Debug)]
struct Counter {
    count: BigUint,
    step: u8,
    offset: u8
}

impl Counter {
    fn new(_step: u8, _offset: u8) -> Counter {
        Counter {count: BigUint::from(0u8), step: _step, offset: _offset}
    }
}

impl Iterator for Counter {
    type Item = BigUint;

    fn next(&mut self) -> Option<BigUint> {
        // Increment our count. This is why we started at zero.
        self.count += self.step;
        Some(self.count.clone())
    }
}

fn main() {
    let start = Instant::now();
    let cpus: u8 = num_cpus::get() as u8;
    println!("{:?}", cpus);

    let barrier = Arc::new(Barrier::new(2));

    for thread in 0..(cpus) {
        let c = barrier.clone();
        thread::spawn(move || {
            println!("Started thread {}!", thread);
            let counter =  Counter::new(cpus-thread, cpus);
            let mut max: u8 = 0;
            for x in counter {
                let n = x.test();
                if n > max {
                    max = n;
                    println!("{} - {}: {}", thread, n, x);
                    if n == 10 {
                        c.wait();
                        return;
                    }
                }
            }
        });
    }
    barrier.wait();
    println!("Finding n = 10 took {:#?}", start.elapsed());
    return;
}