Unwrapping thread index

help
1 
    rayon::spawn(move || {
        (1..=rayon::current_num_threads())
            .into_par_iter()
            .for_each(|_| {
                let result = acme(stuff);
                let idx = rayon::current_thread_index().unwrap();
                let _ = tx.send((idx, result));
            });
    });

Should one really call match or if let for current_thread_index()? Because without spawn the index would not exist, would it? The program would fail even before querying the index.

2

Because without spawn the index would not exist, would it?

Yes, but that's never the case in your code, so there's not much point in handling it. Using unwrap/expect in that scenario is totally fine, imo.

Where matching on it could be useful is if you have code that may or may not be running from a Rayon thread, and you need to do something different based on that.

2 Likes
3

According to the rayon docs, the return value is guaranteed to be Some(_) when called within a rayon worker thread. Hence, unwrapping within such a thread is fine, though I always prefer expect() over unwrap().

Edit: ninja'd

1 Like
4

Unfortunately two solutions aren’t possible. Thanks.

5

Thanks.