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Release rayon 1.2.1 / rayon-core 1.6.1 (2019-11-20)

  • Update crossbeam dependencies.
  • Add top-level doc links for the iterator traits.
  • Document that the iterator traits are not object safe.


Thanks to all of the contributors for this release!

  • @cuviper
  • @dnaka91
  • @matklad
  • @nikomatsakis
  • @Qqwy
  • @vorner

Release rayon 1.2.0 / rayon-core 1.6.0 (2019-08-30)

  • The new ParallelIterator::copied() converts an iterator of references into copied values, like Iterator::copied().
  • ParallelExtend is now implemented for the unit ().
  • Internal updates were made to improve test determinism, reduce closure type sizes, reduce task allocations, and update dependencies.
  • The minimum supported rustc is now 1.28.


Thanks to all of the contributors for this release!

  • @Aaron1011
  • @cuviper
  • @ralfbiedert

Release rayon 1.1.0 / rayon-core 1.5.0 (2019-06-12)

  • FIFO spawns are now supported using the new spawn_fifo() and scope_fifo() global functions, and their corresponding ThreadPool methods.
    • Normally when tasks are queued on a thread, the most recent is processed first (LIFO) while other threads will steal the oldest (FIFO). With FIFO spawns, those tasks are processed locally in FIFO order too.
    • Regular spawns and other tasks like join are not affected.
    • The breadth_first configuration flag, which globally approximated this effect, is now deprecated.
    • For more design details, please see RFC 1.
  • ThreadPoolBuilder can now take a custom spawn_handler to control how threads will be created in the pool.
    • ThreadPoolBuilder::build_scoped() uses this to create a scoped thread pool, where the threads are able to use non-static data.
    • This may also be used to support threading in exotic environments, like WebAssembly, which don't support the normal std::thread.
  • ParallelIterator has 3 new methods: find_map_any(), find_map_first(), and find_map_last(), like Iterator::find_map() with ordering constraints.
  • The new ParallelIterator::panic_fuse() makes a parallel iterator halt as soon as possible if any of its threads panic. Otherwise, the panic state is not usually noticed until the iterator joins its parallel tasks back together.
  • IntoParallelIterator is now implemented for integral RangeInclusive.
  • Several internal Folders now have optimized consume_iter implementations.
  • rayon_core::current_thread_index() is now re-exported in rayon.
  • The minimum rustc is now 1.26, following the update policy defined in RFC 3.


Thanks to all of the contributors for this release!

  • @cuviper
  • @didroe
  • @GuillaumeGomez
  • @huonw
  • @janriemer
  • @kornelski
  • @nikomatsakis
  • @seanchen1991
  • @yegeun542

Release rayon 1.0.3 (2018-11-02)

  • ParallelExtend is now implemented for tuple pairs, enabling nested unzip() and partition_map() operations. For instance, (A, (B, C)) items can be unzipped into (Vec<A>, (Vec<B>, Vec<C>)).
    • ParallelExtend<(A, B)> works like unzip().
    • ParallelExtend<Either<A, B>> works like partition_map().
  • ParallelIterator now has a method map_init() which calls an init function for a value to pair with items, like map_with() but dynamically constructed. That value type has no constraints, not even Send or Sync.
    • The new for_each_init() is a variant of this for simple iteration.
    • The new try_for_each_init() is a variant for fallible iteration.


Thanks to all of the contributors for this release!

  • @cuviper
  • @dan-zheng
  • @dholbert
  • @ignatenkobrain
  • @mdonoughe

Release rayon 1.0.2 / rayon-core 1.4.1 (2018-07-17)

  • The ParallelBridge trait with method par_bridge() makes it possible to use any Sendable Iterator in parallel!
    • This trait has been added to rayon::prelude.
    • It automatically implements internal synchronization and queueing to spread the Items across the thread pool. Iteration order is not preserved by this adaptor.
    • "Native" Rayon iterators like par_iter() should still be preferred when possible for better efficiency.
  • ParallelString now has additional methods for parity with std string iterators: par_char_indices(), par_bytes(), par_encode_utf16(), par_matches(), and par_match_indices().
  • ParallelIterator now has fallible methods try_fold(), try_reduce(), and try_for_each, plus *_with() variants of each, for automatically short-circuiting iterators on None or Err values. These are inspired by Iterator::try_fold() and try_for_each() that were stabilized in Rust 1.27.
  • Range<i128> and Range<u128> are now supported with Rust 1.26 and later.
  • Small improvements have been made to the documentation.
  • rayon-core now only depends on rand for testing.
  • Rayon tests now work on stable Rust.


Thanks to all of the contributors for this release!

  • @AndyGauge
  • @cuviper
  • @ignatenkobrain
  • @LukasKalbertodt
  • @MajorBreakfast
  • @nikomatsakis
  • @paulkernfeld
  • @QuietMisdreavus

Release rayon 1.0.1 (2018-03-16)

  • Added more documentation for rayon::iter::split().
  • Corrected links and typos in documentation.


Thanks to all of the contributors for this release!

  • @cuviper
  • @HadrienG2
  • @matthiasbeyer
  • @nikomatsakis

Release rayon 1.0.0 / rayon-core 1.4.0 (2018-02-15)

  • ParallelIterator added the update method which applies a function to mutable references, inspired by itertools.
  • IndexedParallelIterator added the chunks method which yields vectors of consecutive items from the base iterator, inspired by itertools.
  • String now implements FromParallelIterator<Cow<str>> and ParallelExtend<Cow<str>>, inspired by std.
  • () now implements FromParallelIterator<()>, inspired by std.
  • The new ThreadPoolBuilder replaces and deprecates Configuration.
    • Errors from initialization now have the concrete ThreadPoolBuildError type, rather than Box<Error>, and this type implements Send and Sync.
    • ThreadPool::new is deprecated in favor of ThreadPoolBuilder::build.
    • initialize is deprecated in favor of ThreadPoolBuilder::build_global.
  • Examples have been added to most of the parallel iterator methods.
  • A lot of the documentation has been reorganized and extended.

Breaking changes

  • Rayon now requires rustc 1.13 or greater.
  • IndexedParallelIterator::len and ParallelIterator::opt_len now operate on &self instead of &mut self.
  • IndexedParallelIterator::collect_into is now collect_into_vec.
  • IndexedParallelIterator::unzip_into is now unzip_into_vecs.
  • Rayon no longer exports the deprecated Configuration and initialize from rayon-core.


Thanks to all of the contributors for this release!

  • @Bilkow
  • @cuviper
  • @Enet4
  • @ignatenkobrain
  • @iwillspeak
  • @jeehoonkang
  • @jwass
  • @Kerollmops
  • @KodrAus
  • @kornelski
  • @MaloJaffre
  • @nikomatsakis
  • @obv-mikhail
  • @oddg
  • @phimuemue
  • @stjepang
  • @tmccombs
  • bors[bot]

Release rayon 0.9.0 / rayon-core 1.3.0 / rayon-futures 0.1.0 (2017-11-09)

  • Configuration now has a build method.
  • ParallelIterator added flatten and intersperse, both inspired by itertools.
  • IndexedParallelIterator added interleave, interleave_shortest, and zip_eq, all inspired by itertools.
  • The new functions iter::empty and once create parallel iterators of exactly zero or one item, like their std counterparts.
  • The new functions iter::repeat and repeatn create parallel iterators repeating an item indefinitely or n times, respectively.
  • The new function join_context works like join, with an added FnContext parameter that indicates whether the job was stolen.
  • Either (used by ParallelIterator::partition_map) is now re-exported from the either crate, instead of defining our own type.
    • Either also now implements ParallelIterator, IndexedParallelIterator, and ParallelExtend when both of its Left and Right types do.
  • All public types now implement Debug.
  • Many of the parallel iterators now implement Clone where possible.
  • Much of the documentation has been extended. (but still could use more help!)
  • All rayon crates have improved metadata.
  • Rayon was evaluated in the Libz Blitz, leading to many of these improvements.
  • Rayon pull requests are now guarded by bors-ng.


The spawn_future() method has been refactored into its own rayon-futures crate, now through a ScopeFutureExt trait for ThreadPool and Scope. The supporting rayon-core APIs are still gated by --cfg rayon_unstable.

Breaking changes

  • Two breaking changes have been made to rayon-core, but since they're fixing soundness bugs, we are considering these minor changes for semver.
    • Scope::spawn now requires Send for the closure.
    • ThreadPool::install now requires Send for the return value.
  • The iter::internal module has been renamed to iter::plumbing, to hopefully indicate that while these are low-level details, they're not really internal or private to rayon. The contents of that module are needed for third-parties to implement new parallel iterators, and we'll treat them with normal semver stability guarantees.
  • The function rayon::iter::split is no longer re-exported as rayon::split.


Thanks to all of the contributors for this release!

  • @AndyGauge
  • @ChristopherDavenport
  • @chrisvittal
  • @cuviper
  • @dns2utf8
  • @dtolnay
  • @frewsxcv
  • @gsquire
  • @Hittherhod
  • @jdr023
  • @laumann
  • @leodasvacas
  • @lvillani
  • @MajorBreakfast
  • @mamuleanu
  • @marmistrz
  • @mbrubeck
  • @mgattozzi
  • @nikomatsakis
  • @smt923
  • @stjepang
  • @tmccombs
  • @vishalsodani
  • bors[bot]

Release rayon 0.8.2 (2017-06-28)

  • ParallelSliceMut now has six parallel sorting methods with the same variations as the standard library.
    • par_sort, par_sort_by, and par_sort_by_key perform stable sorts in parallel, using the default order, a custom comparator, or a key extraction function, respectively.
    • par_sort_unstable, par_sort_unstable_by, and par_sort_unstable_by_key perform unstable sorts with the same comparison options.
    • Thanks to @stjepang!

Release rayon 0.8.1 / rayon-core 1.2.0 (2017-06-14)

  • The following core APIs are being stabilized:
    • rayon::spawn() -- spawns a task into the Rayon threadpool; as it is contained in the global scope (rather than a user-created scope), the task cannot capture anything from the current stack frame.
    • ThreadPool::join(), ThreadPool::spawn(), ThreadPool::scope() -- convenience APIs for launching new work within a thread-pool.
  • The various iterator adapters are now tagged with #[must_use]
  • Parallel iterators now offer a for_each_with adapter, similar to map_with.
  • We are adopting a new approach to handling the remaining unstable APIs (which primarily pertain to futures integration). As awlays, unstable APIs are intended for experimentation, but do not come with any promise of compatibility (in other words, we might change them in arbitrary ways in any release). Previously, we designated such APIs using a Cargo feature "unstable". Now, we are using a regular #[cfg] flag. This means that to see the unstable APIs, you must do RUSTFLAGS='--cfg rayon_unstable' cargo build. This is intentionally inconvenient; in particular, if you are a library, then your clients must also modify their environment, signaling their agreement to instability.

Release rayon 0.8.0 / rayon-core 1.1.0 (2017-06-13)

Rayon 0.8.0

  • Added the map_with and fold_with combinators, which help for passing along state (like channels) that cannot be shared between threads but which can be cloned on each thread split.
  • Added the while_some combinator, which helps for writing short-circuiting iterators.
  • Added support for "short-circuiting" collection: e.g., collecting from an iterator producing Option<T> or Result<T, E> into a Option<Collection<T>> or Result<Collection<T>, E>.
  • Support FromParallelIterator for Cow.
  • Removed the deprecated weight APIs.
  • Simplified the parallel iterator trait hierarchy by removing the BoundedParallelIterator and ExactParallelIterator traits, which were not serving much purpose.
  • Improved documentation.
  • Added some missing Send impls.
  • Fixed some small bugs.

Rayon-core 1.1.0

  • We now have more documentation.
  • Renamed the (unstable) methods spawn_async and spawn_future_async -- which spawn tasks that cannot hold references -- to simply spawn and spawn_future, respectively.
  • We are now using the coco library for our deque.
  • Individual threadpools can now be configured in "breadth-first" mode, which causes them to execute spawned tasks in the reverse order that they used to. In some specific scenarios, this can be a win (though it is not generally the right choice).
  • Added top-level functions:
    • current_thread_index, for querying the index of the current worker thread within its thread-pool (previously available as thread_pool.current_thread_index());
    • current_thread_has_pending_tasks, for querying whether the current worker that has an empty task deque or not. This can be useful when deciding whether to spawn a task.
  • The environment variables for controlling Rayon are now RAYON_NUM_THREADS and RAYON_LOG. The older variables (e.g., RAYON_RS_NUM_CPUS are still supported but deprecated).


  • Added a new game-of-life benchmark.


Thanks to the following contributors:

  • @ChristopherDavenport
  • @SuperFluffy
  • @antoinewdg
  • @crazymykl
  • @cuviper
  • @glandium
  • @julian-seward1
  • @leodasvacas
  • @leshow
  • @lilianmoraru
  • @mschmo
  • @nikomatsakis
  • @stjepang

Release rayon 0.7.1 / rayon-core 1.0.2 (2017-05-30)

This release is a targeted performance fix for #343, an issue where rayon threads could sometimes enter into a spin loop where they would be unable to make progress until they are pre-empted.

Release rayon 0.7 / rayon-core 1.0 (2017-04-06)

This release marks the first step towards Rayon 1.0. For best performance, it is important that all Rayon users update to at least Rayon 0.7. This is because, as of Rayon 0.7, we have taken steps to ensure that, no matter how many versions of rayon are actively in use, there will only be a single global scheduler. This is achieved via the rayon-core crate, which is being released at version 1.0, and which encapsulates the core schedule APIs like join(). (Note: the rayon-core crate is, to some degree, an implementation detail, and not intended to be imported directly; it's entire API surface is mirrored through the rayon crate.)

We have also done a lot of work reorganizing the API for Rayon 0.7 in preparation for 1.0. The names of iterator types have been changed and reorganized (but few users are expected to be naming those types explicitly anyhow). In addition, a number of parallel iterator methods have been adjusted to match those in the standard iterator traits more closely. See the "Breaking Changes" section below for details.

Finally, Rayon 0.7 includes a number of new features and new parallel iterator methods. As of this release, Rayon's parallel iterators have officially reached parity with sequential iterators -- that is, every sequential iterator method that makes any sense in parallel is supported in some capacity.

New features and methods

  • The internal Producer trait now features fold_with, which enables better performance for some parallel iterators.
  • Strings now support par_split() and par_split_whitespace().
  • The Configuration API is expanded and simplified:
    • num_threads(0) no longer triggers an error
    • you can now supply a closure to name the Rayon threads that get created by using Configuration::thread_name.
    • you can now inject code when Rayon threads start up and finish
    • you can now set a custom panic handler to handle panics in various odd situations
  • Threadpools are now able to more gracefully put threads to sleep when not needed.
  • Parallel iterators now support find_first(), find_last(), position_first(), and position_last().
  • Parallel iterators now support rev(), which primarily affects subsequent calls to enumerate().
  • The scope() API is now considered stable (and part of rayon-core).
  • There is now a useful rayon::split function for creating custom Rayon parallel iterators.
  • Parallel iterators now allow you to customize the min/max number of items to be processed in a given thread. This mechanism replaces the older weight mechanism, which is deprecated.
  • sum() and friends now use the standard Sum traits

Breaking changes

In the move towards 1.0, there have been a number of minor breaking changes:

  • Configuration setters like Configuration::set_num_threads() lost the set_ prefix, and hence become something like Configuration::num_threads().
  • Configuration getters are removed
  • Iterator types have been shuffled around and exposed more consistently:
    • combinator types live in rayon::iter, e.g. rayon::iter::Filter
    • iterators over various types live in a module named after their type, e.g. rayon::slice::Windows
  • When doing a sum() or product(), type annotations are needed for the result since it is now possible to have the resulting sum be of a type other than the value you are iterating over (this mirrors sequential iterators).

Experimental features

Experimental features require the use of the unstable feature. Their APIs may change or disappear entirely in future releases (even minor releases) and hence they should be avoided for production code.

  • We now have (unstable) support for futures integration. You can use Scope::spawn_future or rayon::spawn_future_async().
  • There is now a rayon::spawn_async() function for using the Rayon threadpool to run tasks that do not have references to the stack.


Thanks to the following people for their contributions to this release:

  • @Aaronepower
  • @ChristopherDavenport
  • @bluss
  • @cuviper
  • @froydnj
  • @gaurikholkar
  • @hniksic
  • @leodasvacas
  • @leshow
  • @martinhath
  • @mbrubeck
  • @nikomatsakis
  • @pegomes
  • @schuster
  • @torkleyy

Release 0.6 (2016-12-21)

This release includes a lot of progress towards the goal of parity with the sequential iterator API, though there are still a few methods that are not yet complete. If you'd like to help with that effort, check out the milestone to see the remaining issues.

Announcement: @cuviper has been added as a collaborator to the Rayon repository for all of his outstanding work on Rayon, which includes both internal refactoring and helping to shape the public API. Thanks @cuviper! Keep it up.

  • We now support collect() and not just collect_with(). You can use collect() to build a number of collections, including vectors, maps, and sets. Moreover, when building a vector with collect(), you are no longer limited to exact parallel iterators. Thanks @nikomatsakis, @cuviper!
  • We now support skip() and take() on parallel iterators. Thanks @martinhath!
  • Breaking change: We now match the sequential APIs for min() and max(). We also support min_by_key() and max_by_key(). Thanks @tapeinosyne!
  • Breaking change: The mul() method is now renamed to product(), to match sequential iterators. Thanks @jonathandturner!
  • We now support parallel iterator over ranges on u64 values. Thanks @cuviper!
  • We now offer a par_chars() method on strings for iterating over characters in parallel. Thanks @cuviper!
  • We now have new demos: a traveling salesman problem solver as well as matrix multiplication. Thanks @nikomatsakis, @edre!
  • We are now documenting our minimum rustc requirement (currently v1.12.0). We will attempt to maintain compatibility with rustc stable v1.12.0 as long as it remains convenient, but if new features are stabilized or added that would be helpful to Rayon, or there are bug fixes that we need, we will bump to the most recent rustc. Thanks @cuviper!
  • The reduce() functionality now has better inlining. Thanks @bluss!
  • The join() function now has some documentation. Thanks @gsquire!
  • The project source has now been fully run through rustfmt. Thanks @ChristopherDavenport!
  • Exposed helper methods for accessing the current thread index. Thanks @bholley!

Release 0.5 (2016-11-04)

  • Breaking change: The reduce method has been vastly simplified, and reduce_with_identity has been deprecated.
  • Breaking change: The fold method has been changed. It used to always reduce the values, but now instead it is a combinator that returns a parallel iterator which can itself be reduced. See the docs for more information.
  • The following parallel iterator combinators are now available (thanks @cuviper!):
    • find_any(): similar to find on a sequential iterator, but doesn't necessarily return the first matching item
    • position_any(): similar to position on a sequential iterator, but doesn't necessarily return the index of first matching item
    • any(), all(): just like their sequential counterparts
  • The count() combinator is now available for parallel iterators.
  • We now build with older versions of rustc again (thanks @durango!), as we removed a stray semicolon from thread_local!.
  • Various improvements to the (unstable) scope() API implementation.

Release 0.4.3 (2016-10-25)

  • Parallel iterators now offer an adaptive weight scheme, which means that explicit weights should no longer be necessary in most cases! Thanks @cuviper!
    • We are considering removing weights or changing the weight mechanism before 1.0. Examples of scenarios where you still need weights even with this adaptive mechanism would be great. Join the discussion at
  • New (unstable) scoped threads API, see rayon::scope for details.
  • The various demos and benchmarks have been consolidated into one program, rayon-demo.
  • Optimizations in Rayon's inner workings. Thanks @emilio!
  • Update num_cpus to 1.0. Thanks @jamwt!
  • Various internal cleanup in the implementation and typo fixes. Thanks @cuviper, @Eh2406, and @spacejam!

Release 0.4.2 (2016-09-15)

  • Updated metadata.

Release 0.4.1 (2016-09-14)

  • New chain combinator for parallel iterators.
  • Option, Result, as well as many more collection types now have parallel iterators.
  • New mergesort demo.
  • Misc fixes.

Thanks to @cuviper, @edre, @jdanford, @frewsxcv for their contributions!

Release 0.4 (2016-05-16)

  • Make use of latest versions of catch-panic and various fixes to panic propagation.
  • Add new prime sieve demo.
  • Add cloned() and inspect() combinators.
  • Misc fixes for Rust RFC 1214.

Thanks to @areilb1, @Amanieu, @SharplEr, and @cuviper for their contributions!

Release 0.3 (2016-02-23)

  • Expanded par_iter APIs now available:
    • into_par_iter is now supported on vectors (taking ownership of the elements)
  • Panic handling is much improved:
    • if you use the Nightly feature, experimental panic recovery is available
    • otherwise, panics propagate out and poision the workpool
  • New Configuration object to control number of threads and other details
  • New demos and benchmarks
    • try cargo run --release -- visualize in demo/nbody :)
      • Note: a nightly compiler is required for this demo due to the use of the += syntax

Thanks to @bjz, @cuviper, @Amanieu, and @willi-kappler for their contributions!

Release 0.2 and earlier

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