Function git_features::parallel::num_threads
source · Available on crate feature
parallel only.Expand description
Returns the amount of threads the system can effectively use as the amount of its logical cores.
Only available with the parallel feature toggle set.
Examples found in repository?
src/parallel/mod.rs (line 147)
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pub fn in_parallel_if<I, S, O, R>(
condition: impl FnOnce() -> bool,
input: impl Iterator<Item = I> + Send,
thread_limit: Option<usize>,
new_thread_state: impl Fn(usize) -> S + Send + Clone,
consume: impl Fn(I, &mut S) -> O + Send + Clone,
reducer: R,
) -> Result<<R as Reduce>::Output, <R as Reduce>::Error>
where
R: Reduce<Input = O>,
I: Send,
O: Send,
{
if num_threads(thread_limit) > 1 && condition() {
in_parallel(input, thread_limit, new_thread_state, consume, reducer)
} else {
serial::in_parallel(input, thread_limit, new_thread_state, consume, reducer)
}
}More examples
src/parallel/in_parallel.rs (line 56)
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pub fn in_parallel<I, S, O, R>(
input: impl Iterator<Item = I> + Send,
thread_limit: Option<usize>,
new_thread_state: impl Fn(usize) -> S + Send + Clone,
consume: impl Fn(I, &mut S) -> O + Send + Clone,
mut reducer: R,
) -> Result<<R as Reduce>::Output, <R as Reduce>::Error>
where
R: Reduce<Input = O>,
I: Send,
O: Send,
{
let num_threads = num_threads(thread_limit);
crossbeam_utils::thread::scope(move |s| {
let receive_result = {
let (send_input, receive_input) = crossbeam_channel::bounded::<I>(num_threads);
let (send_result, receive_result) = crossbeam_channel::bounded::<O>(num_threads);
for thread_id in 0..num_threads {
s.builder()
.name(format!("gitoxide.in_parallel.produce.{thread_id}"))
.spawn({
let send_result = send_result.clone();
let receive_input = receive_input.clone();
let new_thread_state = new_thread_state.clone();
let consume = consume.clone();
move |_| {
let mut state = new_thread_state(thread_id);
for item in receive_input {
if send_result.send(consume(item, &mut state)).is_err() {
break;
}
}
}
})
.expect("valid name");
}
s.builder()
.name("gitoxide.in_parallel.feed".into())
.spawn(move |_| {
for item in input {
if send_input.send(item).is_err() {
break;
}
}
})
.expect("valid name");
receive_result
};
for item in receive_result {
drop(reducer.feed(item)?);
}
reducer.finalize()
})
.expect("no panic")
}
/// An experiment to have fine-grained per-item parallelization with built-in aggregation via thread state.
/// This is only good for operations where near-random access isn't detrimental, so it's not usually great
/// for file-io as it won't make use of sorted inputs well.
/// Note that `periodic` is not guaranteed to be called in case other threads come up first and finish too fast.
// TODO: better docs
pub fn in_parallel_with_slice<I, S, R, E>(
input: &mut [I],
thread_limit: Option<usize>,
new_thread_state: impl FnMut(usize) -> S + Send + Clone,
consume: impl FnMut(&mut I, &mut S) -> Result<(), E> + Send + Clone,
mut periodic: impl FnMut() -> Option<std::time::Duration> + Send,
state_to_rval: impl FnOnce(S) -> R + Send + Clone,
) -> Result<Vec<R>, E>
where
I: Send,
E: Send,
R: Send,
{
let num_threads = num_threads(thread_limit);
let mut results = Vec::with_capacity(num_threads);
let stop_everything = &AtomicBool::default();
let index = &AtomicUsize::default();
// TODO: use std::thread::scope() once Rust 1.63 is available.
crossbeam_utils::thread::scope({
move |s| {
s.builder()
.name("gitoxide.in_parallel_with_slice.watch-interrupts".into())
.spawn({
move |_| loop {
if stop_everything.load(Ordering::Relaxed) {
break;
}
match periodic() {
Some(duration) => std::thread::sleep(duration),
None => {
stop_everything.store(true, Ordering::Relaxed);
break;
}
}
}
})
.expect("valid name");
let input_len = input.len();
struct Input<I>(*mut [I])
where
I: Send;
// SAFETY: I is Send + Sync, so is a *mut [I]
#[allow(unsafe_code)]
unsafe impl<I> Send for Input<I> where I: Send {}
let threads: Vec<_> = (0..num_threads)
.map(|thread_id| {
s.builder()
.name(format!("gitoxide.in_parallel_with_slice.produce.{thread_id}"))
.spawn({
let mut new_thread_state = new_thread_state.clone();
let state_to_rval = state_to_rval.clone();
let mut consume = consume.clone();
let input = Input(input as *mut [I]);
move |_| {
let mut state = new_thread_state(thread_id);
while let Ok(input_index) =
index.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| {
(x < input_len).then(|| x + 1)
})
{
if stop_everything.load(Ordering::Relaxed) {
break;
}
// SAFETY: our atomic counter for `input_index` is only ever incremented, yielding
// each item exactly once.
let item = {
#[allow(unsafe_code)]
unsafe {
&mut (&mut *input.0)[input_index]
}
};
if let Err(err) = consume(item, &mut state) {
stop_everything.store(true, Ordering::Relaxed);
return Err(err);
}
}
Ok(state_to_rval(state))
}
})
.expect("valid name")
})
.collect();
for thread in threads {
match thread.join() {
Ok(res) => {
results.push(res?);
}
Err(err) => {
// a panic happened, stop the world gracefully (even though we panic later)
stop_everything.store(true, Ordering::Relaxed);
std::panic::resume_unwind(err);
}
}
}
stop_everything.store(true, Ordering::Relaxed);
Ok(results)
}
})
.expect("no panic")
}src/parallel/reduce.rs (line 53)
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pub fn new<InputIter, ThreadStateFn, ConsumeFn, I, O, S>(
input: InputIter,
thread_limit: Option<usize>,
new_thread_state: ThreadStateFn,
consume: ConsumeFn,
reducer: Reduce,
) -> Self
where
InputIter: Iterator<Item = I> + Send + 'static,
ThreadStateFn: Fn(usize) -> S + Send + Clone + 'static,
ConsumeFn: Fn(I, &mut S) -> O + Send + Clone + 'static,
Reduce: super::Reduce<Input = O> + 'static,
I: Send + 'static,
O: Send + 'static,
{
let num_threads = num_threads(thread_limit);
let mut threads = Vec::with_capacity(num_threads + 1);
let receive_result = {
let (send_input, receive_input) = crossbeam_channel::bounded::<I>(num_threads);
let (send_result, receive_result) = std::sync::mpsc::sync_channel::<O>(num_threads);
for thread_id in 0..num_threads {
let handle = std::thread::spawn({
let send_result = send_result.clone();
let receive_input = receive_input.clone();
let new_thread_state = new_thread_state.clone();
let consume = consume.clone();
move || {
let mut state = new_thread_state(thread_id);
for item in receive_input {
if send_result.send(consume(item, &mut state)).is_err() {
break;
}
}
}
});
threads.push(handle);
}
threads.push(std::thread::spawn(move || {
for item in input {
if send_input.send(item).is_err() {
break;
}
}
}));
receive_result
};
Stepwise {
threads,
receive_result,
reducer: Some(reducer),
}
}