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85 lines
2.2 KiB
85 lines
2.2 KiB
//! solve the five philosophers problem with monitor
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use std::thread;
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use std::sync::{Mutex, Condvar, Arc};
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use std::time::Duration;
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struct Philosopher {
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name: String,
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left: usize,
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right: usize,
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}
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impl Philosopher {
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fn new(name: &str, left: usize, right: usize) -> Philosopher {
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Philosopher {
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name: name.to_string(),
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left,
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right,
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}
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}
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fn eat(&self, table: &Table) {
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{
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let mut fork_status = table.fork_status.lock().unwrap();
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if fork_status[self.left] {
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fork_status = table.fork_condvar[self.left].wait(fork_status).unwrap()
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}
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fork_status[self.left] = true;
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if fork_status[self.right] {
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fork_status = table.fork_condvar[self.right].wait(fork_status).unwrap()
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}
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fork_status[self.right] = true;
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}
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println!("{} is eating.", self.name);
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thread::sleep(Duration::from_secs(1));
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{
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let mut fork_status = table.fork_status.lock().unwrap();
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fork_status[self.left] = false;
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fork_status[self.right] = false;
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table.fork_condvar[self.left].notify_one();
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table.fork_condvar[self.right].notify_one();
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}
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}
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fn think(&self) {
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println!("{} is thinking.", self.name);
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thread::sleep(Duration::from_secs(1));
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}
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}
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struct Table {
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fork_status: Mutex<Vec<bool>>,
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fork_condvar: Vec<Condvar>,
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}
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// the main function to test
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pub fn main() {
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let table = Arc::new(Table {
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fork_status: Mutex::new(vec![false; 5]),
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fork_condvar: vec![Condvar::new(), Condvar::new(), Condvar::new(), Condvar::new(), Condvar::new()],
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});
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let philosophers = vec![
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Philosopher::new("1", 0, 1),
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Philosopher::new("2", 1, 2),
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Philosopher::new("3", 2, 3),
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Philosopher::new("4", 3, 4),
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Philosopher::new("5", 0, 4),
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];
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let handles: Vec<_> = philosophers.into_iter().map(|p| {
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let table = table.clone();
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thread::spawn(move || {
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for _ in 0..5 {
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p.think();
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p.eat(&table);
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}
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})
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}).collect();
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for h in handles {
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h.join().unwrap();
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}
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} |