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use crate::infallible::Xap;
use crate::runner::ParRunner;
use crate::sizes::SizePair;
use orx_concurrent_iter::{ChunkPuller, ConcurrentIter};
pub fn reduce<Q, I, M, E, X1, X2, S, F>(
_: S,
th_idx: usize,
state: &Q::State,
iter: &I,
x1: X1,
x2: X2,
f: F,
) -> Result<Option<X2::O>, E>
where
Q: ParRunner,
I: ConcurrentIter,
X1: Xap<I = I::Item, O = Result<M, E>>,
X2: Xap<I = M>,
S: SizePair<S1 = X1::Size, S2 = X2::Size>,
F: Fn(X2::O, X2::O) -> X2::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) => {
for a in S::xap_res(x1, x2, i) {
acc = match (a, acc.is_some()) {
(Ok(a), true) => acc.map(|agg| f(agg, a)),
(Ok(a), false) => Some(a),
(Err(e), _) => {
Q::broadcast_stop(iter, state, chunk_state);
return Err(e);
}
};
}
}
// 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) => {
for a in chunk.flat_map(|i| S::xap_res(x1, x2, i)) {
acc = match (a, acc.is_some()) {
(Ok(a), true) => acc.map(|agg| f(agg, a)),
(Ok(a), false) => Some(a),
(Err(e), _) => {
Q::broadcast_stop(iter, state, chunk_state);
return Err(e);
}
};
}
}
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
}
Q::complete_chunk(state, chunk_state);
if acc.is_some() {
break;
}
}
// fold over the aggregate
let result = 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) => {
for a in S::xap_res(x1, x2, i) {
acc = match a {
Ok(a) => f(acc, a),
Err(e) => {
Q::broadcast_stop(iter, state, chunk_state);
return Err(e);
}
};
}
}
// 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) => {
for a in chunk.flat_map(|i| S::xap_res(x1, x2, i)) {
acc = match a {
Ok(a) => f(acc, a),
Err(e) => {
Q::broadcast_stop(iter, state, chunk_state);
return Err(e);
}
};
}
}
None if iter.is_completed_when_none_returned() => break,
None => {}
}
}
}
Q::complete_chunk(state, chunk_state);
}
Some(acc)
}
};
Ok(result)
}