Rust: What is the difference between Rc<T> and Arc<T>?

Rc<T> — reference counting, single-threaded. Arc<T> — atomic reference counting, thread-safe.

Rc<T>:

• Single-threaded only.
• No atomic overhead.
• Faster.

Arc<T>:

• Thread-safe.
• Atomic operations.
• Slightly slower.

1use std::rc::Rc;
2use std::sync::Arc;
3
4// Rc: single thread
5let a = Rc::new(vec![1, 2, 3]);
6let b = Rc::clone(&a);
7
8// Arc: multi-thread
9let a = Arc::new(vec![1, 2, 3]);
10let b = Arc::clone(&a);
11std::thread::spawn(move || println!("{:?}", b));

Key: Rc for single-thread, Arc for multi-thread.