Initial import of rayon-1.5.0. am: 041839ceab am: d836dd6404 am: 7522a9ba00

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rayon/+/1622436

Change-Id: I94b0e06d9da131d6f98db436ad1a178dfff2ec90

1 files changed, 732 insertions, 0 deletions

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+# Release rayon 1.5.0 / rayon-core 1.9.0 (2020-10-21)
+
+- Update crossbeam dependencies.
+- The minimum supported `rustc` is now 1.36.
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @cuviper
+- @mbrubeck
+- @mrksu
+
+# Release rayon 1.4.1 (2020-09-29)
+
+- The new `flat_map_iter` and `flatten_iter` methods can be used to flatten
+  sequential iterators, which may perform better in cases that don't need the
+  nested parallelism of `flat_map` and `flatten`.
+- The new `par_drain` method is a parallel version of the standard `drain` for
+  collections, removing items while keeping the original capacity. Collections
+  that implement this through `ParallelDrainRange` support draining items from
+  arbitrary index ranges, while `ParallelDrainFull` always drains everything.
+- The new `positions` method finds all items that match the given predicate and
+  returns their indices in a new iterator.
+
+# Release rayon-core 1.8.1 (2020-09-17)
+
+- Fixed an overflow panic on high-contention workloads, for a counter that was
+  meant to simply wrap. This panic only occurred with debug assertions enabled,
+  and was much more likely on 32-bit targets.
+
+# Release rayon 1.4.0 / rayon-core 1.8.0 (2020-08-24)
+
+- Implemented a new thread scheduler, [RFC 5], which uses targeted wakeups for
+  new work and for notifications of completed stolen work, reducing wasteful
+  CPU usage in idle threads.
+- Implemented `IntoParallelIterator for Range<char>` and `RangeInclusive<char>`
+  with the same iteration semantics as Rust 1.45.
+- Relaxed the lifetime requirements of the initial `scope` closure.
+
+[RFC 5]: https://github.com/rayon-rs/rfcs/pull/5
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @CAD97
+- @cuviper
+- @kmaork
+- @nikomatsakis
+- @SuperFluffy
+
+
+# Release rayon 1.3.1 / rayon-core 1.7.1 (2020-06-15)
+
+- Fixed a use-after-free race in calls blocked between two rayon thread pools.
+- Collecting to an indexed `Vec` now drops any partial writes while unwinding,
+  rather than just leaking them. If dropping also panics, Rust will abort.
+  - Note: the old leaking behavior is considered _safe_, just not ideal.
+- The new `IndexedParallelIterator::step_by()` adapts an iterator to step
+  through items by the given count, like `Iterator::step_by()`.
+- The new `ParallelSlice::par_chunks_exact()` and mutable equivalent
+  `ParallelSliceMut::par_chunks_exact_mut()` ensure that the chunks always have
+  the exact length requested, leaving any remainder separate, like the slice
+  methods `chunks_exact()` and `chunks_exact_mut()`.
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @adrian5
+- @bluss
+- @cuviper
+- @FlyingCanoe
+- @GuillaumeGomez
+- @matthiasbeyer
+- @picoHz
+- @zesterer
+
+
+# Release rayon 1.3.0 / rayon-core 1.7.0 (2019-12-21)
+
+- Tuples up to length 12 now implement `IntoParallelIterator`, creating a
+  `MultiZip` iterator that produces items as similarly-shaped tuples.
+- The `--cfg=rayon_unstable` supporting code for `rayon-futures` is removed.
+- The minimum supported `rustc` is now 1.31.
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @cuviper
+- @c410-f3r
+- @silwol
+
+
+# Release rayon-futures 0.1.1 (2019-12-21)
+
+- `Send` bounds have been added for the `Item` and `Error` associated types on
+  all generic `F: Future` interfaces. While technically a breaking change, this
+  is a soundness fix, so we are not increasing the semantic version for this.
+- This crate is now deprecated, and the `--cfg=rayon_unstable` supporting code
+  will be removed in `rayon-core 1.7.0`. This only supported the now-obsolete
+  `Future` from `futures 0.1`, while support for `std::future::Future` is
+  expected to come directly in `rayon-core` -- although that is not ready yet.
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @cuviper
+- @kornelski
+- @jClaireCodesStuff
+- @jwass
+- @seanchen1991
+
+
+# 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.
+
+## Contributors
+
+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.
+
+## Contributors
+
+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 `Folder`s 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].
+
+## Contributors
+
+Thanks to all of the contributors for this release!
+
+- @cuviper
+- @didroe
+- @GuillaumeGomez
+- @huonw
+- @janriemer
+- @kornelski
+- @nikomatsakis
+- @seanchen1991
+- @yegeun542
+
+[RFC 1]: https://github.com/rayon-rs/rfcs/blob/master/accepted/rfc0001-scope-scheduling.md
+[RFC 3]: https://github.com/rayon-rs/rfcs/blob/master/accepted/rfc0003-minimum-rustc.md
+
+
+# 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.
+
+## Contributors
+
+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 `Send`able `Iterator` in parallel!
+  - This trait has been added to `rayon::prelude`.
+  - It automatically implements internal synchronization and queueing to
+    spread the `Item`s 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.
+
+## Contributors
+
+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.
+
+## Contributors
+
+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.
+
+## Contributors
+
+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.
+
+## Futures
+
+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`.
+
+## Contributors
+
+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).
+
+## Rayon-demo
+
+- Added a new game-of-life benchmark.
+
+## Contributors
+
+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.
+
+### Contributors
+
+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](https://github.com/nikomatsakis/rayon/issues?q=is%3Aopen+is%3Aissue+milestone%3A%22Parity+with+the+%60Iterator%60+trait%22)
+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 <https://github.com/nikomatsakis/rayon/issues/111>.
+- New (unstable) scoped threads API, see `rayon::scope` for details.
+  - You will need to supply the [cargo feature] `unstable`.
+- 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!
+
+[cargo feature]: http://doc.crates.io/manifest.html#the-features-section
+
+
+# Release 0.4.2 (2016-09-15)
+
+- Updated crates.io 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
+
+No release notes were being kept at this time.