Module rayon::iter[−][src]

Traits for writing parallel programs using an iterator-style interface

You will rarely need to interact with this module directly unless you have need to name one of the iterator types.

Parallel iterators make it easy to write iterator-like chains that execute in parallel: typically all you have to do is convert the first .iter() (or iter_mut(), into_iter(), etc) method into par_iter() (or par_iter_mut(), into_par_iter(), etc). For example, to compute the sum of the squares of a sequence of integers, one might write:

use rayon::prelude::*;
fn sum_of_squares(input: &[i32]) -> i32 {
    input.par_iter()
         .map(|i| i * i)
         .sum()
}

Or, to increment all the integers in a slice, you could write:

use rayon::prelude::*;
fn increment_all(input: &mut [i32]) {
    input.par_iter_mut()
         .for_each(|p| *p += 1);
}

To use parallel iterators, first import the traits by adding something like use rayon::prelude::* to your module. You can then call par_iter, par_iter_mut, or into_par_iter to get a parallel iterator. Like a regular iterator, parallel iterators work by first constructing a computation and then executing it.

In addition to par_iter() and friends, some types offer other ways to create (or consume) parallel iterators:

Slices (&[T], &mut [T]) offer methods like par_split and par_windows, as well as various parallel sorting operations. See the ParallelSlice trait for the full list.
Strings (&str) offer methods like par_split and par_lines. See the ParallelString trait for the full list.
Various collections offer par_extend, which grows a collection given a parallel iterator. (If you don’t have a collection to extend, you can use collect() to create a new one from scratch.)

To see the full range of methods available on parallel iterators, check out the ParallelIterator and IndexedParallelIterator traits.

If you’d like to build a custom parallel iterator, or to write your own combinator, then check out the split function and the plumbing module.

Note: Several of the ParallelIterator methods rely on a Try trait which has been deliberately obscured from the public API. This trait is intended to mirror the unstable std::ops::Try with implementations for Option and Result, where Some/Ok values will let those iterators continue, but None/Err values will exit early.

A note about object safety: It is currently not possible to wrap a ParallelIterator (or any trait that depends on it) using a Box<dyn ParallelIterator> or other kind of dynamic allocation, because ParallelIterator is not object-safe. (This keeps the implementation simpler and allows extra optimizations.)

Modules

plumbing

Traits and functions used to implement parallel iteration. These are low-level details – users of parallel iterators should not need to interact with them directly. See the plumbing README for a general overview.

Structs

Chain	`Chain` is an iterator that joins `b` after `a` in one continuous iterator. This struct is created by the `chain()` method on `ParallelIterator`
Chunks	`Chunks` is an iterator that groups elements of an underlying iterator.
Cloned	`Cloned` is an iterator that clones the elements of an underlying iterator.
Copied	`Copied` is an iterator that copies the elements of an underlying iterator.
Empty	Iterator adaptor for the `empty()` function.
Enumerate	`Enumerate` is an iterator that returns the current count along with the element. This struct is created by the `enumerate()` method on `IndexedParallelIterator`
Filter	`Filter` takes a predicate `filter_op` and filters out elements that match. This struct is created by the `filter()` method on `ParallelIterator`
FilterMap	`FilterMap` creates an iterator that uses `filter_op` to both filter and map elements. This struct is created by the `filter_map()` method on `ParallelIterator`.
FlatMap	`FlatMap` maps each element to a parallel iterator, then flattens these iterators together. This struct is created by the `flat_map()` method on `ParallelIterator`
FlatMapIter	`FlatMapIter` maps each element to a serial iterator, then flattens these iterators together. This struct is created by the `flat_map_iter()` method on `ParallelIterator`
Flatten	`Flatten` turns each element to a parallel iterator, then flattens these iterators together. This struct is created by the `flatten()` method on `ParallelIterator`.
FlattenIter	`FlattenIter` turns each element to a serial iterator, then flattens these iterators together. This struct is created by the `flatten_iter()` method on `ParallelIterator`.
Fold	`Fold` is an iterator that applies a function over an iterator producing a single value. This struct is created by the `fold()` method on `ParallelIterator`
FoldWith	`FoldWith` is an iterator that applies a function over an iterator producing a single value. This struct is created by the `fold_with()` method on `ParallelIterator`
Inspect	`Inspect` is an iterator that calls a function with a reference to each element before yielding it.
Interleave	`Interleave` is an iterator that interleaves elements of iterators `i` and `j` in one continuous iterator. This struct is created by the `interleave()` method on `IndexedParallelIterator`
InterleaveShortest	`InterleaveShortest` is an iterator that works similarly to `Interleave`, but this version stops returning elements once one of the iterators run out.
Intersperse	`Intersperse` is an iterator that inserts a particular item between each item of the adapted iterator. This struct is created by the `intersperse()` method on `ParallelIterator`
IterBridge	`IterBridge` is a parallel iterator that wraps a sequential iterator.
Map	`Map` is an iterator that transforms the elements of an underlying iterator.
MapInit	`MapInit` is an iterator that transforms the elements of an underlying iterator.
MapWith	`MapWith` is an iterator that transforms the elements of an underlying iterator.
MaxLen	`MaxLen` is an iterator that imposes a maximum length on iterator splits. This struct is created by the `max_len()` method on `IndexedParallelIterator`
MinLen	`MinLen` is an iterator that imposes a minimum length on iterator splits. This struct is created by the `min_len()` method on `IndexedParallelIterator`
MultiZip	`MultiZip` is an iterator that zips up a tuple of parallel iterators to produce tuples of their items.
Once	Iterator adaptor for the `once()` function.
PanicFuse	`PanicFuse` is an adaptor that wraps an iterator with a fuse in case of panics, to halt all threads as soon as possible.
Positions	`Positions` takes a predicate `predicate` and filters out elements that match, yielding their indices.
Repeat	Iterator adaptor for the `repeat()` function.
RepeatN	Iterator adaptor for the `repeatn()` function.
Rev	`Rev` is an iterator that produces elements in reverse order. This struct is created by the `rev()` method on `IndexedParallelIterator`
Skip	`Skip` is an iterator that skips over the first `n` elements. This struct is created by the `skip()` method on `IndexedParallelIterator`
Split	`Split` is a parallel iterator using arbitrary data and a splitting function. This struct is created by the `split()` function.
StepBy	`StepBy` is an iterator that skips `n` elements between each yield, where `n` is the given step. This struct is created by the `step_by()` method on `IndexedParallelIterator`
Take	`Take` is an iterator that iterates over the first `n` elements. This struct is created by the `take()` method on `IndexedParallelIterator`
TryFold	`TryFold` is an iterator that applies a function over an iterator producing a single value. This struct is created by the `try_fold()` method on `ParallelIterator`
TryFoldWith	`TryFoldWith` is an iterator that applies a function over an iterator producing a single value. This struct is created by the `try_fold_with()` method on `ParallelIterator`
Update	`Update` is an iterator that mutates the elements of an underlying iterator before they are yielded.
WhileSome	`WhileSome` is an iterator that yields the `Some` elements of an iterator, halting as soon as any `None` is produced.
Zip	`Zip` is an iterator that zips up `a` and `b` into a single iterator of pairs. This struct is created by the `zip()` method on `IndexedParallelIterator`
ZipEq	An `IndexedParallelIterator` that iterates over two parallel iterators of equal length simultaneously.

Enums

Either

The enum Either with variants Left and Right is a general purpose sum type with two cases.

Traits

FromParallelIterator	`FromParallelIterator` implements the creation of a collection from a `ParallelIterator`. By implementing `FromParallelIterator` for a given type, you define how it will be created from an iterator.
IndexedParallelIterator	An iterator that supports “random access” to its data, meaning that you can split it at arbitrary indices and draw data from those points.
IntoParallelIterator	`IntoParallelIterator` implements the conversion to a `ParallelIterator`.
IntoParallelRefIterator	`IntoParallelRefIterator` implements the conversion to a `ParallelIterator`, providing shared references to the data.
IntoParallelRefMutIterator	`IntoParallelRefMutIterator` implements the conversion to a `ParallelIterator`, providing mutable references to the data.
ParallelBridge	Conversion trait to convert an `Iterator` to a `ParallelIterator`.
ParallelDrainFull	`ParallelDrainFull` creates a parallel iterator that moves all items from a collection while retaining the original capacity.
ParallelDrainRange	`ParallelDrainRange` creates a parallel iterator that moves a range of items from a collection while retaining the original capacity.
ParallelExtend	`ParallelExtend` extends an existing collection with items from a `ParallelIterator`.
ParallelIterator	Parallel version of the standard iterator trait.

Functions

empty	Creates a parallel iterator that produces nothing.
once	Creates a parallel iterator that produces an element exactly once.
repeat	Creates a parallel iterator that endlessly repeats `elt` (by cloning it). Note that this iterator has “infinite” length, so typically you would want to use `zip` or `take` or some other means to shorten it, or consider using the `repeatn()` function instead.
repeatn	Creates a parallel iterator that produces `n` repeats of `elt` (by cloning it).
split	The `split` function takes arbitrary data and a closure that knows how to split it, and turns this into a `ParallelIterator`.