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//! Parallel iterator types for [ranges][std::range],
//! the type for values created by `a..b` expressions
//!
//! You will rarely need to interact with this module directly unless you have
//! need to name one of the iterator types.
//!
//! ```
//! use rayon::prelude::*;
//!
//! let r = (0..100u64).into_par_iter()
//! .sum();
//!
//! // compare result with sequential calculation
//! assert_eq!((0..100).sum::<u64>(), r);
//! ```
//!
use crate::iter::plumbing::*;
use crate::iter::*;
use std::ops::Range;
/// Parallel iterator over a range, implemented for all integer types and `char`.
///
/// **Note:** The `zip` operation requires `IndexedParallelIterator`
/// which is not implemented for `u64`, `i64`, `u128`, or `i128`.
///
/// ```
/// use rayon::prelude::*;
///
/// let p = (0..25usize).into_par_iter()
/// .zip(0..25usize)
/// .filter(|&(x, y)| x % 5 == 0 || y % 5 == 0)
/// .map(|(x, y)| x * y)
/// .sum::<usize>();
///
/// let s = (0..25usize).zip(0..25)
/// .filter(|&(x, y)| x % 5 == 0 || y % 5 == 0)
/// .map(|(x, y)| x * y)
/// .sum();
///
/// assert_eq!(p, s);
/// ```
#[derive(Debug, Clone)]
pub struct Iter<T> {
range: Range<T>,
}
/// Implemented for ranges of all primitive integer types and `char`.
impl<T> IntoParallelIterator for Range<T>
where
Iter<T>: ParallelIterator,
{
type Item = <Iter<T> as ParallelIterator>::Item;
type Iter = Iter<T>;
fn into_par_iter(self) -> Self::Iter {
Iter { range: self }
}
}
struct IterProducer<T> {
range: Range<T>,
}
impl<T> IntoIterator for IterProducer<T>
where
Range<T>: Iterator,
{
type Item = <Range<T> as Iterator>::Item;
type IntoIter = Range<T>;
fn into_iter(self) -> Self::IntoIter {
self.range
}
}
/// These traits help drive integer type inference. Without them, an unknown `{integer}` type only
/// has constraints on `Iter<{integer}>`, which will probably give up and use `i32`. By adding
/// these traits on the item type, the compiler can see a more direct constraint to infer like
/// `{integer}: RangeInteger`, which works better. See `test_issue_833` for an example.
///
/// They have to be `pub` since they're seen in the public `impl ParallelIterator` constraints, but
/// we put them in a private modules so they're not actually reachable in our public API.
mod private {
use super::*;
/// Implementation details of `ParallelIterator for Iter<Self>`
pub trait RangeInteger: Sized + Send {
private_decl! {}
fn drive_unindexed<C>(iter: Iter<Self>, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self>;
fn opt_len(iter: &Iter<Self>) -> Option<usize>;
}
/// Implementation details of `IndexedParallelIterator for Iter<Self>`
pub trait IndexedRangeInteger: RangeInteger {
private_decl! {}
fn drive<C>(iter: Iter<Self>, consumer: C) -> C::Result
where
C: Consumer<Self>;
fn len(iter: &Iter<Self>) -> usize;
fn with_producer<CB>(iter: Iter<Self>, callback: CB) -> CB::Output
where
CB: ProducerCallback<Self>;
}
}
use private::{IndexedRangeInteger, RangeInteger};
impl<T: RangeInteger> ParallelIterator for Iter<T> {
type Item = T;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<T>,
{
T::drive_unindexed(self, consumer)
}
#[inline]
fn opt_len(&self) -> Option<usize> {
T::opt_len(self)
}
}
impl<T: IndexedRangeInteger> IndexedParallelIterator for Iter<T> {
fn drive<C>(self, consumer: C) -> C::Result
where
C: Consumer<T>,
{
T::drive(self, consumer)
}
#[inline]
fn len(&self) -> usize {
T::len(self)
}
fn with_producer<CB>(self, callback: CB) -> CB::Output
where
CB: ProducerCallback<T>,
{
T::with_producer(self, callback)
}
}
macro_rules! indexed_range_impl {
( $t:ty ) => {
impl RangeInteger for $t {
private_impl! {}
fn drive_unindexed<C>(iter: Iter<$t>, consumer: C) -> C::Result
where
C: UnindexedConsumer<$t>,
{
bridge(iter, consumer)
}
fn opt_len(iter: &Iter<$t>) -> Option<usize> {
Some(iter.range.len())
}
}
impl IndexedRangeInteger for $t {
private_impl! {}
fn drive<C>(iter: Iter<$t>, consumer: C) -> C::Result
where
C: Consumer<$t>,
{
bridge(iter, consumer)
}
fn len(iter: &Iter<$t>) -> usize {
iter.range.len()
}
fn with_producer<CB>(iter: Iter<$t>, callback: CB) -> CB::Output
where
CB: ProducerCallback<$t>,
{
callback.callback(IterProducer { range: iter.range })
}
}
impl Producer for IterProducer<$t> {
type Item = <Range<$t> as Iterator>::Item;
type IntoIter = Range<$t>;
fn into_iter(self) -> Self::IntoIter {
self.range
}
fn split_at(self, index: usize) -> (Self, Self) {
assert!(index <= self.range.len());
// For signed $t, the length and requested index could be greater than $t::MAX, and
// then `index as $t` could wrap to negative, so wrapping_add is necessary.
let mid = self.range.start.wrapping_add(index as $t);
let left = self.range.start..mid;
let right = mid..self.range.end;
(IterProducer { range: left }, IterProducer { range: right })
}
}
};
}
trait UnindexedRangeLen<L> {
fn len(&self) -> L;
}
macro_rules! unindexed_range_impl {
( $t:ty, $len_t:ty ) => {
impl UnindexedRangeLen<$len_t> for Range<$t> {
fn len(&self) -> $len_t {
let &Range { start, end } = self;
if end > start {
end.wrapping_sub(start) as $len_t
} else {
0
}
}
}
impl RangeInteger for $t {
private_impl! {}
fn drive_unindexed<C>(iter: Iter<$t>, consumer: C) -> C::Result
where
C: UnindexedConsumer<$t>,
{
#[inline]
fn offset(start: $t) -> impl Fn(usize) -> $t {
move |i| start.wrapping_add(i as $t)
}
if let Some(len) = iter.opt_len() {
// Drive this in indexed mode for better `collect`.
(0..len)
.into_par_iter()
.map(offset(iter.range.start))
.drive(consumer)
} else {
bridge_unindexed(IterProducer { range: iter.range }, consumer)
}
}
fn opt_len(iter: &Iter<$t>) -> Option<usize> {
usize::try_from(iter.range.len()).ok()
}
}
impl UnindexedProducer for IterProducer<$t> {
type Item = $t;
fn split(mut self) -> (Self, Option<Self>) {
let index = self.range.len() / 2;
if index > 0 {
let mid = self.range.start.wrapping_add(index as $t);
let right = mid..self.range.end;
self.range.end = mid;
(self, Some(IterProducer { range: right }))
} else {
(self, None)
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
folder.consume_iter(self)
}
}
};
}
// all Range<T> with ExactSizeIterator
indexed_range_impl! {u8}
indexed_range_impl! {u16}
indexed_range_impl! {u32}
indexed_range_impl! {usize}
indexed_range_impl! {i8}
indexed_range_impl! {i16}
indexed_range_impl! {i32}
indexed_range_impl! {isize}
// other Range<T> with just Iterator
unindexed_range_impl! {u64, u64}
unindexed_range_impl! {i64, u64}
unindexed_range_impl! {u128, u128}
unindexed_range_impl! {i128, u128}
// char is special because of the surrogate range hole
macro_rules! convert_char {
( $self:ident . $method:ident ( $( $arg:expr ),* ) ) => {{
let start = $self.range.start as u32;
let end = $self.range.end as u32;
if start < 0xD800 && 0xE000 < end {
// chain the before and after surrogate range fragments
(start..0xD800)
.into_par_iter()
.chain(0xE000..end)
.map(|codepoint| unsafe { char::from_u32_unchecked(codepoint) })
.$method($( $arg ),*)
} else {
// no surrogate range to worry about
(start..end)
.into_par_iter()
.map(|codepoint| unsafe { char::from_u32_unchecked(codepoint) })
.$method($( $arg ),*)
}
}};
}
impl ParallelIterator for Iter<char> {
type Item = char;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
convert_char!(self.drive(consumer))
}
fn opt_len(&self) -> Option<usize> {
Some(self.len())
}
}
impl IndexedParallelIterator for Iter<char> {
// Split at the surrogate range first if we're allowed to
fn drive<C>(self, consumer: C) -> C::Result
where
C: Consumer<Self::Item>,
{
convert_char!(self.drive(consumer))
}
fn len(&self) -> usize {
// Taken from <char as Step>::steps_between
let start = self.range.start as u32;
let end = self.range.end as u32;
if start < end {
let mut count = end - start;
if start < 0xD800 && 0xE000 <= end {
count -= 0x800
}
count as usize
} else {
0
}
}
fn with_producer<CB>(self, callback: CB) -> CB::Output
where
CB: ProducerCallback<Self::Item>,
{
convert_char!(self.with_producer(callback))
}
}
#[test]
fn check_range_split_at_overflow() {
// Note, this split index overflows i8!
let producer = IterProducer { range: -100i8..100 };
let (left, right) = producer.split_at(150);
let r1: i32 = left.range.map(i32::from).sum();
let r2: i32 = right.range.map(i32::from).sum();
assert_eq!(r1 + r2, -100);
}
#[test]
fn test_i128_len_doesnt_overflow() {
// Using parse because some versions of rust don't allow long literals
let octillion: i128 = "1000000000000000000000000000".parse().unwrap();
let producer = IterProducer {
range: 0..octillion,
};
assert_eq!(octillion as u128, producer.range.len());
assert_eq!(octillion as u128, (0..octillion).len());
assert_eq!(2 * octillion as u128, (-octillion..octillion).len());
assert_eq!(u128::MAX, (i128::MIN..i128::MAX).len());
}
#[test]
fn test_u64_opt_len() {
assert_eq!(Some(100), (0..100u64).into_par_iter().opt_len());
assert_eq!(
Some(usize::MAX),
(0..usize::MAX as u64).into_par_iter().opt_len()
);
if (usize::MAX as u64) < u64::MAX {
assert_eq!(
None,
(0..(usize::MAX as u64).wrapping_add(1))
.into_par_iter()
.opt_len()
);
assert_eq!(None, (0..u64::MAX).into_par_iter().opt_len());
}
}
#[test]
fn test_u128_opt_len() {
assert_eq!(Some(100), (0..100u128).into_par_iter().opt_len());
assert_eq!(
Some(usize::MAX),
(0..usize::MAX as u128).into_par_iter().opt_len()
);
assert_eq!(None, (0..1 + usize::MAX as u128).into_par_iter().opt_len());
assert_eq!(None, (0..u128::MAX).into_par_iter().opt_len());
}
// `usize as i64` can overflow, so make sure to wrap it appropriately
// when using the `opt_len` "indexed" mode.
#[test]
#[cfg(target_pointer_width = "64")]
fn test_usize_i64_overflow() {
use crate::ThreadPoolBuilder;
let iter = (-2..i64::MAX).into_par_iter();
assert_eq!(iter.opt_len(), Some(i64::MAX as usize + 2));
// always run with multiple threads to split into, or this will take forever...
let pool = ThreadPoolBuilder::new().num_threads(8).build().unwrap();
pool.install(|| assert_eq!(iter.find_last(|_| true), Some(i64::MAX - 1)));
}
#[test]
fn test_issue_833() {
fn is_even(n: i64) -> bool {
n % 2 == 0
}
// The integer type should be inferred from `is_even`
let v: Vec<_> = (1..100).into_par_iter().filter(|&x| is_even(x)).collect();
assert!(v.into_iter().eq((2..100).step_by(2)));
// Try examples with indexed iterators too
let pos = (0..100).into_par_iter().position_any(|x| x == 50i16);
assert_eq!(pos, Some(50usize));
assert!((0..100)
.into_par_iter()
.zip(0..100)
.all(|(a, b)| i16::eq(&a, &b)));
}