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Diffstat (limited to 'third_party/rust/rayon/src/iter/fold_chunks.rs')
| -rw-r--r-- | third_party/rust/rayon/src/iter/fold_chunks.rs | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/third_party/rust/rayon/src/iter/fold_chunks.rs b/third_party/rust/rayon/src/iter/fold_chunks.rs new file mode 100644 index 0000000000..185fb1a65d --- /dev/null +++ b/third_party/rust/rayon/src/iter/fold_chunks.rs @@ -0,0 +1,236 @@ +use std::fmt::{self, Debug}; + +use super::chunks::ChunkProducer; +use super::plumbing::*; +use super::*; +use crate::math::div_round_up; + +/// `FoldChunks` is an iterator that groups elements of an underlying iterator and applies a +/// function over them, producing a single value for each group. +/// +/// This struct is created by the [`fold_chunks()`] method on [`IndexedParallelIterator`] +/// +/// [`fold_chunks()`]: trait.IndexedParallelIterator.html#method.fold_chunks +/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html +#[must_use = "iterator adaptors are lazy and do nothing unless consumed"] +#[derive(Clone)] +pub struct FoldChunks<I, ID, F> +where + I: IndexedParallelIterator, +{ + base: I, + chunk_size: usize, + fold_op: F, + identity: ID, +} + +impl<I: IndexedParallelIterator + Debug, ID, F> Debug for FoldChunks<I, ID, F> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Fold") + .field("base", &self.base) + .field("chunk_size", &self.chunk_size) + .finish() + } +} + +impl<I, ID, U, F> FoldChunks<I, ID, F> +where + I: IndexedParallelIterator, + ID: Fn() -> U + Send + Sync, + F: Fn(U, I::Item) -> U + Send + Sync, + U: Send, +{ + /// Creates a new `FoldChunks` iterator + pub(super) fn new(base: I, chunk_size: usize, identity: ID, fold_op: F) -> Self { + FoldChunks { + base, + chunk_size, + identity, + fold_op, + } + } +} + +impl<I, ID, U, F> ParallelIterator for FoldChunks<I, ID, F> +where + I: IndexedParallelIterator, + ID: Fn() -> U + Send + Sync, + F: Fn(U, I::Item) -> U + Send + Sync, + U: Send, +{ + type Item = U; + + fn drive_unindexed<C>(self, consumer: C) -> C::Result + where + C: Consumer<U>, + { + bridge(self, consumer) + } + + fn opt_len(&self) -> Option<usize> { + Some(self.len()) + } +} + +impl<I, ID, U, F> IndexedParallelIterator for FoldChunks<I, ID, F> +where + I: IndexedParallelIterator, + ID: Fn() -> U + Send + Sync, + F: Fn(U, I::Item) -> U + Send + Sync, + U: Send, +{ + fn len(&self) -> usize { + div_round_up(self.base.len(), self.chunk_size) + } + + fn drive<C>(self, consumer: C) -> C::Result + where + C: Consumer<Self::Item>, + { + bridge(self, consumer) + } + + fn with_producer<CB>(self, callback: CB) -> CB::Output + where + CB: ProducerCallback<Self::Item>, + { + let len = self.base.len(); + return self.base.with_producer(Callback { + chunk_size: self.chunk_size, + len, + identity: self.identity, + fold_op: self.fold_op, + callback, + }); + + struct Callback<CB, ID, F> { + chunk_size: usize, + len: usize, + identity: ID, + fold_op: F, + callback: CB, + } + + impl<T, CB, ID, U, F> ProducerCallback<T> for Callback<CB, ID, F> + where + CB: ProducerCallback<U>, + ID: Fn() -> U + Send + Sync, + F: Fn(U, T) -> U + Send + Sync, + { + type Output = CB::Output; + + fn callback<P>(self, base: P) -> CB::Output + where + P: Producer<Item = T>, + { + let identity = &self.identity; + let fold_op = &self.fold_op; + let fold_iter = move |iter: P::IntoIter| iter.fold(identity(), fold_op); + let producer = ChunkProducer::new(self.chunk_size, self.len, base, fold_iter); + self.callback.callback(producer) + } + } + } +} + +#[cfg(test)] +mod test { + use super::*; + use std::ops::Add; + + #[test] + fn check_fold_chunks() { + let words = "bishbashbosh!" + .chars() + .collect::<Vec<_>>() + .into_par_iter() + .fold_chunks(4, String::new, |mut s, c| { + s.push(c); + s + }) + .collect::<Vec<_>>(); + + assert_eq!(words, vec!["bish", "bash", "bosh", "!"]); + } + + // 'closure' values for tests below + fn id() -> i32 { + 0 + } + fn sum<T, U>(x: T, y: U) -> T + where + T: Add<U, Output = T>, + { + x + y + } + + #[test] + #[should_panic(expected = "chunk_size must not be zero")] + fn check_fold_chunks_zero_size() { + let _: Vec<i32> = vec![1, 2, 3] + .into_par_iter() + .fold_chunks(0, id, sum) + .collect(); + } + + #[test] + fn check_fold_chunks_even_size() { + assert_eq!( + vec![1 + 2 + 3, 4 + 5 + 6, 7 + 8 + 9], + (1..10) + .into_par_iter() + .fold_chunks(3, id, sum) + .collect::<Vec<i32>>() + ); + } + + #[test] + fn check_fold_chunks_empty() { + let v: Vec<i32> = vec![]; + let expected: Vec<i32> = vec![]; + assert_eq!( + expected, + v.into_par_iter() + .fold_chunks(2, id, sum) + .collect::<Vec<i32>>() + ); + } + + #[test] + fn check_fold_chunks_len() { + assert_eq!(4, (0..8).into_par_iter().fold_chunks(2, id, sum).len()); + assert_eq!(3, (0..9).into_par_iter().fold_chunks(3, id, sum).len()); + assert_eq!(3, (0..8).into_par_iter().fold_chunks(3, id, sum).len()); + assert_eq!(1, (&[1]).par_iter().fold_chunks(3, id, sum).len()); + assert_eq!(0, (0..0).into_par_iter().fold_chunks(3, id, sum).len()); + } + + #[test] + fn check_fold_chunks_uneven() { + let cases: Vec<(Vec<u32>, usize, Vec<u32>)> = vec![ + ((0..5).collect(), 3, vec![0 + 1 + 2, 3 + 4]), + (vec![1], 5, vec![1]), + ((0..4).collect(), 3, vec![0 + 1 + 2, 3]), + ]; + + for (i, (v, n, expected)) in cases.into_iter().enumerate() { + let mut res: Vec<u32> = vec![]; + v.par_iter() + .fold_chunks(n, || 0, sum) + .collect_into_vec(&mut res); + assert_eq!(expected, res, "Case {} failed", i); + + res.truncate(0); + v.into_par_iter() + .fold_chunks(n, || 0, sum) + .rev() + .collect_into_vec(&mut res); + assert_eq!( + expected.into_iter().rev().collect::<Vec<u32>>(), + res, + "Case {} reversed failed", + i + ); + } + } +} |