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multithreading - 如何使用 self 中的方法使用函数？

问题描述

在尝试编写一些并行代码时，我不断遇到如下错误。我找到了一些解决方案，但它们都涉及我不想做的锁定。有什么办法可以解决这个问题吗？

pub trait PermBrute {
    fn quadgram( &self, max_len: usize, ciphertext: &String ) -> Vec<usize> {
        let mut vec : Vec<(f64, Vec<usize>)> = Vec::new();
        let results = Arc::new(Mutex::new(vec));
        let mut threads = vec![];

        for i in 0..*CPUS {
            threads.push( thread::spawn({
                let clone = Arc::clone(&results);
                let text = ciphertext.clone();
                move || {
                    // some code here
                    let hold = self.decrypt( )
                    // some more code here

                    let mut v = clone.lock().unwrap();
                    v.push(best_key);
                }
            }));
        }

        for t in threads {
            t.join().unwrap();
        }

        let lock = Arc::try_unwrap(results).expect("Lock still has multiple owners");
        let mut hold = lock.into_inner().expect("Mutex cannot be locked");

        // do some stuff with hold and return out

        return out;
    }

    fn decrypt( &self, ciphertext : &String, key : &Vec<usize>) -> String;
}

error[E0277]: `Self` cannot be shared between threads safely
   --> src/ciphers/cipher.rs:131:27
    |
108 |     fn quadgram( &self, max_len: usize, ciphertext: &String ) -> Vec<usize> {
    |                                                                            - help: consider further restricting `Self`: `where Self: std::marker::Sync`
...
131 |             threads.push( thread::spawn({
    |                           ^^^^^^^^^^^^^ `Self` cannot be shared between threads safely
    |
    = help: the trait `std::marker::Sync` is not implemented for `Self`
    = note: required because of the requirements on the impl of `std::marker::Send` for `&Self`
    = note: required because it appears within the type `[closure@src/ciphers/cipher.rs:140:17: 164:18 text:std::string::String, start_len:usize, end_len:usize, count:usize, start_points_clone:std::vec::Vec<usize>, local_self:&Self, end:usize, clone:std::sync::Arc<std::sync::Mutex<std::vec::Vec<(f64, std::vec::Vec<usize>)>>>]`

标签： multithreadingrustparallel-processingrayon

解决方案

使用rayon crate，这可以使用并行迭代器技术来完成。

pub trait PermBrute {
    fn quadgram(&self, max_len: usize, ciphertext: &String) -> Vec<usize> {
        let mut vec: Vec<(f64, Vec<usize>)> = Vec::new();
        let mut threads = vec![];
        
        let best_keys: Vec<_> = (0..*CPUS)
            .into_par_iter()
            .map(|i| {
                // some code here
                // you can access `ciphertext` here directly without copying
                todo!();
                // some more code here
                
                best_key
            })
            .collect();

        // do some stuff with best_keys and return out

        return out;
    }
    fn decrypt(&self, ciphertext: &String, key: &Vec<usize>) -> String;
}

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