CODEWITHSUNDEEP
multithreadingrust
user1949917
user1949917

Reputation:

Future::spawn() kinda useless? How can I multi-thread this?

Excerpt from main here:

let value: Value = json::from_str(&sbuf).unwrap();
let coords = value.find("coordinates").unwrap().as_array().unwrap();
let x = Future::spawn(|| coords.iter().fold(0f64, |mut a,b| { a += read_coord_value(&b, "x"); a }));
let y = Future::spawn(|| coords.iter().fold(0f64, |mut a,b| { a += read_coord_value(&b, "y"); a }));
let z = Future::spawn(|| coords.iter().fold(0f64, |mut a,b| { a += read_coord_value(&b, "z"); a }));

println!("x: {}; y: {}; z: {}",
         x.await().unwrap(),
         y.await().unwrap(),
         z.await().unwrap());

So, basically, what I'm doing here won't work because this spawn call requires everything that is passed to it to have a static lifetime--which means that there is basically no work I can avoid repeating. At all. Pointless.

What's a good way to do threading here?

Upvotes: 1

Views: 125

Answers (1)

Levans
Levans

Reputation: 15002

Here, to properly do a multithreading, you need to used scoped threads, with std::thread::scoped(..).

These threads do not need a 'static closure to execute, but they must be joined.

For example:

use std::thread::scoped;

fn main() {
    let coords = [(1f64,2f64,3f64),(1.,2.,3.),(1.,2.,3.),(1.,2.,3.)];
    let x = scoped(|| coords.iter().fold(0f64, |mut a,b| { a += b.0; a }));
    let y = scoped(|| coords.iter().fold(0f64, |mut a,b| { a += b.1; a }));
    let z = scoped(|| coords.iter().fold(0f64, |mut a,b| { a += b.2; a }));

    println!("x: {}; y: {}; z: {}",
             x.join(),
             y.join(),
             z.join());
}

Upvotes: 2

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