CODEWITHSUNDEEP
rustrayon
Timmmm
Timmmm

Reputation: 96586

How to process Results with Rayon parallel iterator?

The .lines() iterator in Rust yields Result<&str>s, so you need to do something like this:

let file = File::open("foo")?;
let reader = BufReader::new(file);

let output: Vec<...> = reader
        .lines()
        .map(|line| line.unwrap())
        .map(|line| process_string(line))
        .collect();

Except of course, .unwrap() sucks, so I solved this with process_results:

let output: Vec<...> = reader
        .lines()
        .process_results(|ok_lines| ok_lines.map(|line| process_string(line)).collect())?;

This works perfectly. But now I want to do the processing in parallel with Rayon.

let output: Vec<...> = reader
        .lines()
        .par_bridge()
        .map(|line| line.unwrap())
        .map(|line| process_string(line))
        .collect();

Again this works great, but now... how do I process it in parallel without unwrap()?

I basically want par_process_results() but it doesn't seem to exist. Rayon's ParallelIterator has a few try_ methods like try_fold() but there doesn't seem to be a try_map() or try_collect().

Upvotes: 0

Views: 47

Answers (1)

Timmmm
Timmmm

Reputation: 96586

Oh I forgot about the .collect trick. This works:

let output: Vec<...> = reader
        .lines()
        .par_bridge()
        .map(|line| Ok(process_string(line?)))
        .collect::<Result<Vec<_>, _>>()?;

Upvotes: 0

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