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|
/// A task pool abstraction. Useful for achieving predictable CPU
/// parallelism.
use pipes::{Chan, Port};
use task::{SchedMode, SingleThreaded};
enum Msg<T> {
Execute(~fn(&T)),
Quit
}
pub struct TaskPool<T> {
channels: ~[Chan<Msg<T>>],
mut next_index: uint,
drop {
for self.channels.each |channel| {
channel.send(Quit);
}
}
}
pub impl<T> TaskPool<T> {
/// Spawns a new task pool with `n_tasks` tasks. If the `sched_mode`
/// is None, the tasks run on this scheduler; otherwise, they run on a
/// new scheduler with the given mode. 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.
static fn new(n_tasks: uint,
opt_sched_mode: Option<SchedMode>,
init_fn_factory: ~fn() -> ~fn(uint) -> T) -> TaskPool<T> {
assert n_tasks >= 1;
let channels = do vec::from_fn(n_tasks) |i| {
let (chan, port) = pipes::stream::<Msg<T>>();
let init_fn = init_fn_factory();
let task_body: ~fn() = |move port, move init_fn| {
let local_data = init_fn(i);
loop {
match port.recv() {
Execute(move f) => f(&local_data),
Quit => break
}
}
};
// Start the task.
match opt_sched_mode {
None => {
// Run on this scheduler.
task::spawn(move task_body);
}
Some(sched_mode) => {
task::task().sched_mode(sched_mode).spawn(move task_body);
}
}
move chan
};
return TaskPool { channels: move 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`.
fn execute(&self, f: ~fn(&T)) {
self.channels[self.next_index].send(Execute(move f));
self.next_index += 1;
if self.next_index == self.channels.len() { self.next_index = 0; }
}
}
#[test]
fn test_task_pool() {
let f: ~fn() -> ~fn(uint) -> uint = || {
let g: ~fn(uint) -> uint = |i| i;
move g
};
let pool = TaskPool::new(4, Some(SingleThreaded), move f);
for 8.times {
pool.execute(|i| io::println(fmt!("Hello from thread %u!", *i)));
}
}
|
