Deep copies of Mutex<> in Rust?

May 28, 2023

I have to generate a large Vec<Mutex<...>> at the start of each iteration in my loop which gets mutated in the loop. Since regenerating it each iteration is quite expensive, I am looking for some way to initialize the vec only once, and make deep clones of the vector to use in the loop. Of course a simple .clone() won’t work because the clone will still mutex-guard the same data in memory, not make copies of it. Something along the lines of

let my_vec = (0..big_usize).map(|_| Mutex::new(..)).collect();

for ... {
    clone = my_vec.deep_clone();
    mutate_clone_safely();
}

>Solution :

As pointed out by kmdreko in the comments, the deep_clone you’re looking for could be implemented like this:

fn deep_clone<T: Clone>(v: &[Mutex<T>]) -> Vec<Mutex<T>> {
    v.iter()
        .map(|el| Mutex::new(el.lock().unwrap().clone()))
        .collect()
}