multithreading - 将矩阵 (Vec>) 只读传递给多个线程

Question

我是 Rust 的新手，我正在为借用的概念而苦苦挣扎。

我想加载 Vec<Vec<f64>>矩阵，然后并行处理它。但是，当我尝试编译这段代码时，我得到了 error: capture of moved value: `matrix` [E0382]在 let _ =行。

这个矩阵对于线程来说应该是只读的，他们不会修改它。如何以只读方式传递它并消除“移动值”错误？

fn process(matrix: &Vec<Vec<f64>>) {
    // do nothing for now
}

fn test() {
    let filename = "matrix.tsv";
    // loads matrix into a Vec<Vec<f64>>
    let mut matrix = load_matrix(filename);

    // Determine number of cpus
    let ncpus = num_cpus::get();
    println!("Number of cpus on this machine: {}", ncpus);
    for i in 0..ncpus {
        // In the next line the "error: capture of moved value: matrix" happens
        let _ = thread::spawn(move || {
            println!("Thread number: {}", i);
            process(&matrix);
        });
    }
    let d = Duration::from_millis(1000 * 1000);
    thread::sleep(d);
}

Answer 1

将要共享的对象包装到 Arc 中，它代表原子引用计数(指针)。对于每个线程，克隆此指针并将克隆的所有权传递给线程。被包装的对象在不再被任何东西使用时将被释放。

fn process(matrix: &Vec<Vec<f64>>) {
    // do nothing for now
}

fn test() {
    use std::sync::Arc;
    let filename = "matrix.tsv";
    // loads matrix into a Vec<Vec<f64>>
    let mut matrix = Arc::new(load_matrix(filename));

    // Determine number of cpus
    let ncpus = num_cpus::get();
    println!("Number of cpus on this machine: {}", ncpus);
    for i in 0..ncpus {
        let matrix = matrix.clone();
        let _ = thread::spawn(move || {
            println!("Thread number: {}", i);
            process(&matrix);
        });
    }
    let d = Duration::from_millis(1000 * 1000);
    thread::sleep(d);
}