四.计算

use std::{
    sync::{Arc, Mutex},
    thread::spawn,
};

use rand::{thread_rng, Rng};

fn main() {
    const COUNT: i32 = 100000000;
    const NUM: i32 = 12;
    let counter = Arc::new(Mutex::new(0));
    let mut handles = vec![];
    for k in 0..NUM {
        let count = counter.clone();
        let hander = spawn(move || {
            for v in 0..COUNT {
                let mut rand = thread_rng();
                let x = rand.gen::<f32>();
                let y = rand.gen::<f32>();
                if x * x + y * y <= 1.0 {
                    let mut s = count.lock().unwrap();
                    *s += 1
                }
            }
        });
        handles.push(hander)
    }

    for v in handles {
        v.join().unwrap()
    }
    let count = 4.0 * *counter.lock().unwrap() as f64;
    println!("dddd {} dddd", count / (COUNT * NUM) as f64)
}