anor_utils/
threadpool.rs

1//! Thread Pool
2//! The implementation is taken from the [book](https://doc.rust-lang.org/book/ch20-02-multithreaded.html)
3
4use std::{
5    sync::{mpsc, Arc, Mutex},
6    thread,
7};
8
9type Job = Box<dyn FnOnce() + Send + 'static>;
10
11pub struct ThreadPool {
12    workers: Vec<Worker>,
13    sender: Option<mpsc::Sender<Job>>,
14}
15
16struct Worker {
17    id: usize,
18    thread: Option<thread::JoinHandle<()>>,
19}
20
21impl Drop for ThreadPool {
22    fn drop(&mut self) {
23        drop(self.sender.take());
24
25        for worker in &mut self.workers {
26            if log::log_enabled!(log::Level::Trace) {
27                log::trace!("Shutting down worker {}", worker.id);
28            }
29            if let Some(thread) = worker.thread.take() {
30                thread.join().unwrap();
31            }
32        }
33    }
34}
35
36impl ThreadPool {
37    /// Create a new ThreadPool.
38    ///
39    /// The size is the number of threads in the pool.
40    ///
41    /// # Panics
42    ///
43    /// The `new` function will panic if the size is zero.
44    pub fn new(size: usize) -> ThreadPool {
45        assert!(size > 0);
46
47        let (sender, receiver) = mpsc::channel();
48
49        let receiver = Arc::new(Mutex::new(receiver));
50
51        let mut workers = Vec::with_capacity(size);
52
53        for id in 0..size {
54            workers.push(Worker::new(id, receiver.clone()));
55        }
56
57        ThreadPool {
58            workers,
59            sender: Some(sender),
60        }
61    }
62
63    pub fn execute<F>(&self, f: F)
64    where
65        F: FnOnce() + Send + 'static,
66    {
67        let job = Box::new(f);
68
69        self.sender.as_ref().unwrap().send(job).unwrap();
70    }
71
72    /// blocks the executor and waits for the completion of active jobs
73    pub fn wait_for_completion(&self) {
74        todo!()
75    }
76}
77
78impl Worker {
79    fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
80        let thread = thread::spawn(move || loop {
81            let message = receiver.lock().unwrap().recv();
82
83            match message {
84                Ok(job) => {
85                    if log::log_enabled!(log::Level::Trace) {
86                        log::trace!("Worker {id} got a job; executing.");
87                    }
88
89                    job();
90                }
91                Err(_) => {
92                    if log::log_enabled!(log::Level::Trace) {
93                        log::trace!("Worker {id} disconnected; shutting down.");
94                    }
95                    break;
96                }
97            }
98        });
99
100        Worker {
101            id,
102            thread: Some(thread),
103        }
104    }
105}
106
107#[cfg(test)]
108pub mod test {
109
110    use std::time::Duration;
111
112    use super::*;
113
114    #[test]
115    fn thread_pool_test() {
116        use std::sync::atomic::{AtomicU64, Ordering};
117
118        let total = Arc::new(AtomicU64::new(0));
119
120        // need a scope to drop the pool and join threads
121        {
122            let pool = ThreadPool::new(4);
123            let task = |n: u64| {
124                thread::sleep(Duration::from_millis(20));
125                n * n
126            };
127
128            for n in 0..100 {
129                let total_clone = total.clone();
130                pool.execute(move || {
131                    let product = task(n);
132                    total_clone.fetch_add(product, Ordering::SeqCst);
133                });
134            }
135        }
136        
137        // wait for executed threads complete
138        // pool.wait_for_completion();
139        // drop(pool);
140
141        assert_eq!(total.load(Ordering::SeqCst), 328350);
142    }
143}
anor_utils/threadpool.rs

anor_utils/
threadpool.rs
