Rust Concurrency and Parallelism

Are you ready to take your Rust programming skills to the next level? One of the most exciting and rewarding areas to explore is concurrency and parallelism. In this article, we'll dive into the world of Rust concurrency and parallelism -- what they are, why they matter, and how they can help you write faster, more efficient code.

What is Concurrency?

So, what is concurrency? Simply put, it's the ability of a program to perform multiple tasks at the same time. This is in contrast to a program that performs tasks in a sequential manner -- one after the other. When a program can perform multiple tasks simultaneously, it can take advantage of the full power of a multi-core processor.

Why is Concurrency Important?

In today's world of computing, multi-core processors are the norm. They provide a huge boost in computing power, but they can only be fully utilized if a program is able to perform tasks concurrently. In addition, many applications have to deal with slow I/O operations like reading from a file or querying a database. By using concurrency, these tasks can be performed in the background while the program continues to execute other tasks. This can lead to significant improvements in performance and responsiveness.

Types of Concurrency

In Rust, there are two main types of concurrency: threads and coroutines. Threads are essentially lightweight processes that run simultaneously within a program. Coroutines, on the other hand, are lightweight threads that run cooperatively within a single thread. They take turns executing their tasks, yielding control to other coroutines when necessary.


Rust's threading system is based on the standard Thread API provided by the operating system. This means that Rust's threads are essentially just lightweight wrappers around the operating system's threads. Creating a new thread in Rust is as simple as calling the thread::spawn function and passing a closure that contains the code to be run in the new thread.

Here's an example:

use std::thread;

fn main() {
    let handle = thread::spawn(|| {
        // Code to be run in the new thread

    // Wait for the thread to finish

In this example, we're creating a new thread and passing a closure that contains the code to be run in the new thread. We're also calling the join method on the thread handle to wait for the thread to finish executing.


Rust's coroutine system is based on the async/await syntax introduced in Rust 1.39. Coroutines in Rust are created using the async keyword, which marks a function that can be run cooperatively with other coroutines.

Here's an example:

async fn coroutine() {
    // Code to be run in the coroutine

async fn main() {
    let result = coroutine().await;

In this example, we're creating a new coroutine using the async keyword. We're also using the Tokio runtime to execute the coroutine. Coroutines in Rust are designed to be lightweight and highly efficient, making them ideal for tasks that require high concurrency.

What is Parallelism?

So, we've talked about concurrency -- but what about parallelism? Parallelism is the ability of a program to perform multiple tasks simultaneously across multiple processors or cores. This is in contrast to concurrency, which allows a program to perform multiple tasks at the same time on a single processor or core.

Why is Parallelism Important?

As we mentioned earlier, modern computers almost always have multiple processors or cores. By taking advantage of parallelism, a program can utilize all of the available computing power and perform tasks more quickly and efficiently.

Types of Parallelism

In Rust, there are two main types of parallelism: data parallelism and task parallelism. Data parallelism involves dividing a large data set into smaller pieces and processing each piece simultaneously. Task parallelism involves dividing a program into smaller tasks and running each task on a separate processor or core.

Data Parallelism

In Rust, data parallelism can be achieved using the Rayon library. Rayon provides a simple, high-level API for parallelizing data processing tasks. Here's an example:

use rayon::prelude::*;

fn main() {
    let data = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    let result = data.par_iter().sum::<i32>();
    println!("{}", result);

In this example, we're creating a vector of integers and using the par_iter method provided by Rayon to parallelize the processing of the vector. The sum method then sums up all of the integers in the vector and returns the result.

Task Parallelism

In Rust, task parallelism can be achieved using the futures and Tokio libraries. Futures provide a powerful programming model for asynchronous tasks, while Tokio provides a runtime for executing tasks in a highly concurrent manner. Here's an example:

use futures::future::join_all;

async fn task_one() {
    // Code for task one

async fn task_two() {
    // Code for task two

async fn task_three() {
    // Code for task three

async fn main() {
    let tasks = vec![task_one(), task_two(), task_three()];
    let results = join_all(tasks).await;

In this example, we're creating three asynchronous tasks using the async keyword and the Tokio runtime. We're then using the join_all method provided by the futures library to run all of the tasks in parallel and wait for them to finish executing. The results variable contains the results of all three tasks.


As we've seen, concurrency and parallelism are powerful programming techniques that can help make Rust programs faster and more efficient. By using threads, coroutines, data parallelism, and task parallelism, Rust developers can take full advantage of the power of modern computing hardware. So why not explore these techniques in your own Rust projects? With a little practice and experimentation, you'll be amazed at what you can accomplish.

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