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task_pool.rs
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task_pool.rs
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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Abstraction of a task pool for basic parallelism.
use core::prelude::*;
use task;
use task::spawn;
use vec::Vec;
use comm::{channel, Sender};
enum Msg<T> {
Execute(proc(&T):Send),
Quit
}
/// A task pool used to execute functions in parallel.
pub struct TaskPool<T> {
channels: Vec<Sender<Msg<T>>>,
next_index: uint,
}
#[unsafe_destructor]
impl<T> Drop for TaskPool<T> {
fn drop(&mut self) {
for channel in self.channels.mut_iter() {
channel.send(Quit);
}
}
}
impl<T> TaskPool<T> {
/// Spawns a new task pool with `n_tasks` tasks. The provided
/// `init_fn_factory` returns a function which, given the index of the
/// task, should return local data to be kept around in that task.
///
/// # Failure
///
/// This function will fail if `n_tasks` is less than 1.
pub fn new(n_tasks: uint,
init_fn_factory: || -> proc(uint):Send -> T)
-> TaskPool<T> {
assert!(n_tasks >= 1);
let channels = Vec::from_fn(n_tasks, |i| {
let (tx, rx) = channel::<Msg<T>>();
let init_fn = init_fn_factory();
let task_body = proc() {
let local_data = init_fn(i);
loop {
match rx.recv() {
Execute(f) => f(&local_data),
Quit => break
}
}
};
// Run on this scheduler.
task::spawn(task_body);
tx
});
return TaskPool {
channels: channels,
next_index: 0,
};
}
/// Executes the function `f` on a task in the pool. The function
/// receives a reference to the local data returned by the `init_fn`.
pub fn execute(&mut self, f: proc(&T):Send) {
self.channels.get(self.next_index).send(Execute(f));
self.next_index += 1;
if self.next_index == self.channels.len() { self.next_index = 0; }
}
}
#[test]
fn test_task_pool() {
let f: || -> proc(uint):Send -> uint = || { proc(i) i };
let mut pool = TaskPool::new(4, f);
for _ in range(0, 8) {
pool.execute(proc(i) println!("Hello from thread {}!", *i));
}
}
#[test]
#[should_fail]
fn test_zero_tasks_failure() {
let f: || -> proc(uint):Send -> uint = || { proc(i) i };
TaskPool::new(0, f);
}