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|0.3.1||Mar 11, 2021|
|0.1.1||Jun 6, 2018|
#139 in Concurrency
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Used in 60 crates (5 directly)
Note: This is an unstable fork made for use in rustc
Rayon-core represents the "core, stable" APIs of Rayon: join, scope, and so forth, as well as the ability to create custom thread-pools with ThreadPool.
Maybe worth mentioning: users are not necessarily intended to directly access rayon-core; all its APIs are mirror in the rayon crate. To that end, the examples in the docs use rayon::join and so forth rather than rayon_core::join.
rayon-core aims to never, or almost never, have a breaking change to its API, because each revision of rayon-core also houses the global thread-pool (and hence if you have two simultaneous versions of rayon-core, you have two thread-pools).
Please see Rayon Docs for details about using Rayon.
Rayon-core currently requires
rustc 1.59.0 or greater.
Rayon-core houses the core stable APIs of Rayon.
These APIs have been mirrored in the Rayon crate and it is recommended to use these from there.
join is used to take two closures and potentially run them in parallel.
- It will run in parallel if task B gets stolen before task A can finish.
- It will run sequentially if task A finishes before task B is stolen and can continue on task B.
scope creates a scope in which you can run any number of parallel tasks.
These tasks can spawn nested tasks and scopes, but given the nature of work stealing, the order of execution can not be guaranteed.
The scope will exist until all tasks spawned within the scope have been completed.
spawn add a task into the 'static' or 'global' scope, or a local scope created by the
ThreadPool can be used to create your own thread pools (using
ThreadPoolBuilder) or to customize the global one.
Tasks spawned within the pool (using
join(), etc.) will be added to a deque,
where it becomes available for work stealing from other threads in the local threadpool.
Global fallback when threading is unsupported
std APIs for threading, but some targets have incomplete implementations that
Unsupported errors. The WebAssembly
targets are notable examples of this. Rather than panicking on the unsupported error when
creating the implicit global threadpool, Rayon configures a fallback mode instead.
This fallback mode mostly functions as if it were using a single-threaded "pool", like setting
RAYON_NUM_THREADS=1. For example,
join will execute its two closures sequentially, since
there is no other thread to share the work. However, since the pool is not running independent
of the main thread, non-blocking calls like
spawn may not execute at all, unless a lower-
priority call like
broadcast gives them an opening. The fallback mode does not try to emulate
anything like thread preemption or
async task switching, but
can also volunteer execution time.
ThreadPoolBuilder methods always report their error without any fallback.
Restricting multiple versions
In order to ensure proper coordination between threadpools, and especially
to make sure there's only one global threadpool,
rayon-core is actively
restricted from building multiple versions of itself into a single target.
You may see a build error like this in violation:
error: native library `rayon-core` is being linked to by more than one package, and can only be linked to by one package
While we strive to keep
rayon-core semver-compatible, it's still
possible to arrive at this situation if different crates have overly
restrictive tilde or inequality requirements for
conflicting requirements will need to be resolved before the build will