rustlings/exercises/smart_pointers/arc1.rs

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// arc1.rs
//
// In this exercise, we are given a Vec of u32 called "numbers" with values
// ranging from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ] We would like to use this
// set of numbers within 8 different threads simultaneously. Each thread is
// going to get the sum of every eighth value, with an offset.
//
// The first thread (offset 0), will sum 0, 8, 16, ...
// The second thread (offset 1), will sum 1, 9, 17, ...
// The third thread (offset 2), will sum 2, 10, 18, ...
// ...
// The eighth thread (offset 7), will sum 7, 15, 23, ...
//
// Because we are using threads, our values need to be thread-safe. Therefore,
// we are using Arc. We need to make a change in each of the two TODOs.
//
// Make this code compile by filling in a value for `shared_numbers` where the
// first TODO comment is, and create an initial binding for `child_numbers`
// where the second TODO comment is. Try not to create any copies of the
// `numbers` Vec!
//
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// Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
#![forbid(unused_imports)] // Do not change this, (or the next) line.
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use std::sync::Arc;
use std::thread;
fn main() {
let numbers: Vec<_> = (0..100u32).collect();
let shared_numbers = // TODO
let mut joinhandles = Vec::new();
for offset in 0..8 {
let child_numbers = // TODO
joinhandles.push(thread::spawn(move || {
let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
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println!("Sum of offset {} is {}", offset, sum);
}));
}
for handle in joinhandles.into_iter() {
handle.join().unwrap();
}
}