• Rust8.2 Fearless Concurrency 无畏并发


    Rust学习笔记

    Rust编程语言入门教程课程笔记

    参考教材: The Rust Programming Language (by Steve Klabnik and Carol Nichols, with contributions from the Rust Community)

    Lecture 16: Fearless Concurrency 无畏并发

    src/main.rs

    use std::thread;
    use std::time::Duration;
    use std::sync::mpsc;
    use std::sync::{Mutex, Arc};
    
    fn main() {
        //Using Threads to Run Code Simultaneously
    
        //Creating a New Thread with spawn
        
        let handle = thread::spawn(|| {
            for i in 1..10 {
                println!("hi number {} from the spawned thread!", i);
                thread::sleep(Duration::from_millis(1));
            }
        });
    
        for i in 1..5 {
            println!("hi number {} from the main thread!", i);
            thread::sleep(Duration::from_millis(1));
        }
        // output:
        // hi number 1 from the main thread!
        // hi number 1 from the spawned thread!
        // hi number 2 from the main thread!
        // hi number 2 from the spawned thread!
        // hi number 3 from the main thread!
        // hi number 3 from the spawned thread!
        // hi number 4 from the main thread!
        // hi number 4 from the spawned thread!
    
        //In this run, the main thread printed first, 
        //even though the print statement from the spawned thread appears first in the code. 
        //And even though we told the spawned thread to print until i is 9, 
        //it only got to 5 before the main thread shut down.
    
        //Waiting for All Threads to Finish Using join Handles
        handle.join().unwrap();
        
        let v = vec![1, 2, 3];
        let handle = thread::spawn(move || {
            println!("Here's a vector: {:?}", v);
        });//move closure: v is moved into the closure
    
        // drop(v); // oh no! v is moved into the thread
    
        handle.join().unwrap();
    
        //Using Message Passing to Transfer Data Between Threads
        let (tx, rx) = mpsc::channel();
        thread::spawn(move || {
            let val = String::from("hi");
            // tx.send(val).unwrap();
            tx.send(val).unwrap();
            // println!("val is {}", val); // error: value borrowed here after move
        });
    
        let received = rx.recv().unwrap();//recv blocks the main thread’s execution and waits until a value is sent down the channel
        println!("Got: {}", received);
    
        //try_recv: without blocking
        
        //Sending Multiple Values and Seeing the Receiver Waiting
        let (tx, rx) = mpsc::channel();
        thread::spawn(move || {
            let vals = vec![
                String::from("hello"),
                String::from("from"),
                String::from("the"),
                String::from("thread"),];
            for val in vals {
                tx.send(val).unwrap();
                thread::sleep(Duration::from_secs(1));
            }
        });
    
        for received in rx {
            println!("Got: {}", received);
        }
    
        //Shared-State Concurrency
        //Mutexes: Mutual Exclusion
        //API: lock, unwrap, Mutex (smart pointer)
    
        let m = Mutex::new(5);
        {
            let mut num = m.lock().unwrap();
            *num = 6;
            // println!("m is {}", m); // error: cannot be formatted with the default formatter
        }
    
        println!("m is {:?}", m);
    
        //Sharing a Mutex Between Multiple Threads
        let counter = Arc::new(Mutex::new(0));
        //Arc is an atomically reference counted type
        //A: atomically, R: reference, C: counted
        //API in Arc is the same as in Rc 
    
    
        let mut handles = vec![];
    
        for _ in 0..10 {
            let counter = Arc::clone(&counter);
            let handle = thread::spawn(move || {
                let mut num = counter.lock().unwrap();
    
                *num += 1;
            });
            handles.push(handle);
        }
    
        for handle in handles {
            handle.join().unwrap();
        }
    
        println!("Result: {}", *counter.lock().unwrap());//Result: 10
    
        //Extensible Concurrency with the Sync and Send Traits
        //Send: ownership can be transferred between threads
        //Sync: multiple threads can have references to the same value
    
        //Implementing Send and Sync Manually Is Unsafe
    }
    
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  • 原文地址:https://blog.csdn.net/weixin_45347752/article/details/134496062