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use crate::infallible::xap::Xap;
use crate::runner::ParRunner;
use orx_concurrent_iter::{ChunkPuller, ConcurrentIter};
pub fn reduce<Q, I, X, F>(th_idx: usize, state: &Q::State, iter: &I, x: X, f: F) -> Option<X::O>
where
Q: ParRunner,
I: ConcurrentIter,
X: Xap<I = I::Item>,
F: Fn(X::O, X::O) -> X::O,
{
let mut chunk_puller = iter.chunk_puller_by(0, th_idx);
let mut acc = None;
// discover first aggregate
loop {
let chunk_size = Q::next_chunk_size(state, iter.size_hint());
let chunk_state = Q::begin_chunk(th_idx, chunk_size);
match chunk_size {
0 | 1 => {
match iter.next_by(th_idx) {
Some(i) => {
let result = x.xap(i).into_iter().reduce(&f);
if result.is_some() {
acc = result;
break;
}
}
// TODO: a good back-off strategy might be used, needs benchmark with ConcurrentQueue
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
c => {
chunk_puller.resize_for_chunk_size(c);
match chunk_puller.pull() {
Some(chunk) => {
let result = chunk.flat_map(|i| x.xap(i)).reduce(&f);
if result.is_some() {
acc = result;
break;
}
}
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
}
Q::complete_chunk(state, chunk_state);
}
// fold over the aggregate
match acc {
None => None,
Some(mut acc) => {
loop {
let chunk_size = Q::next_chunk_size(state, iter.size_hint());
let chunk_state = Q::begin_chunk(th_idx, chunk_size);
match chunk_size {
0 | 1 => {
match iter.next_by(th_idx) {
Some(i) => {
let result = x.xap(i).into_iter().reduce(&f);
if let Some(y) = result {
acc = f(acc, y);
}
}
// TODO: a good back-off strategy might be used, needs benchmark with ConcurrentQueue
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
c => {
chunk_puller.resize_for_chunk_size(c);
match chunk_puller.pull() {
Some(chunk) => {
let result = chunk.flat_map(|i| x.xap(i)).reduce(&f);
if let Some(y) = result {
acc = f(acc, y);
}
}
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
}
Q::complete_chunk(state, chunk_state);
}
Some(acc)
}
}
}