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In the src/bin folder, create a file called parallelism.rs
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Add the following code and run it with cargo run --bin parallelism
1 use std::thread;
2
3 fn main() {
4 // Spawning a thread lets it execute a lambda
5 let child = thread::spawn(|| println!("Hello from a new
thread!"));
6 println!("Hello from the main thread!");
7 // Joining a child thread with the main thread means
8 // that the main thread waits until the child has
9 // finished it's work
10 child.join().expect("Failed to join the child thread");
11
12 let sum = parallel_sum(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
13 println!("The sum of the numbers 1 to 10 is {}", sum);
14 }
15
16 // We are going to write a function that
17 // sums the numbers in a slice in parallel
18 fn parallel_sum(range: &[i32]) -> i32 {
19 // We are going to use exactly 4 threads to sum the numbers
20 const NUM_THREADS: usize = 4;
21
22 // If we have less numbers than threads,
23 // there's no point in multithreading them
24 if range.len() < NUM_THREADS {
25 sum_bucket(range)
26 } else {
27 // We define "bucket" as the amount of numbers
28 // we sum in a single thread
29 let bucket_size = range.len() / NUM_THREADS;
30 let mut count = 0;
31 // This vector will keep track of our threads
32 let mut threads = Vec::new();
33 // We try to sum as much as possible in other threads
34 while count + bucket_size < range.len() {
35 let bucket = range[count..count +
bucket_size].to_vec();
36 let thread = thread::Builder::new()
37 .name("calculation".to_string())
38 .spawn(move || sum_bucket(&bucket))
39 .expect("Failed to create the thread");
40 threads.push(thread);
41
42 count += bucket_size
43 }
44 // We are going to sum the rest in the main thread
45 let mut sum = sum_bucket(&range[count..]);
46
47 // Time to add the results up
48 for thread in threads {
49 sum += thread.join().expect("Failed to join thread");
50 }
51 sum
52 }
53 }
54
55 // This is the function that will be executed in the threads
56 fn sum_bucket(range: &[i32]) -> i32 {
57 let mut sum = 0;
58 for num in range {
59 sum += *num;
60 }
61 sum
62 }