rayon_core/broadcast/
mod.rs

1use crate::job::{ArcJob, StackJob};
2use crate::latch::{CountLatch, LatchRef};
3use crate::registry::{Registry, WorkerThread};
4use std::fmt;
5use std::marker::PhantomData;
6use std::sync::Arc;
7
8mod test;
9
10/// Executes `op` within every thread in the current threadpool. If this is
11/// called from a non-Rayon thread, it will execute in the global threadpool.
12/// Any attempts to use `join`, `scope`, or parallel iterators will then operate
13/// within that threadpool. When the call has completed on each thread, returns
14/// a vector containing all of their return values.
15///
16/// For more information, see the [`ThreadPool::broadcast()`][m] method.
17///
18/// [m]: struct.ThreadPool.html#method.broadcast
19pub fn broadcast<OP, R>(op: OP) -> Vec<R>
20where
21    OP: Fn(BroadcastContext<'_>) -> R + Sync,
22    R: Send,
23{
24    // We assert that current registry has not terminated.
25    unsafe { broadcast_in(op, &Registry::current()) }
26}
27
28/// Spawns an asynchronous task on every thread in this thread-pool. This task
29/// will run in the implicit, global scope, which means that it may outlast the
30/// current stack frame -- therefore, it cannot capture any references onto the
31/// stack (you will likely need a `move` closure).
32///
33/// For more information, see the [`ThreadPool::spawn_broadcast()`][m] method.
34///
35/// [m]: struct.ThreadPool.html#method.spawn_broadcast
36pub fn spawn_broadcast<OP>(op: OP)
37where
38    OP: Fn(BroadcastContext<'_>) + Send + Sync + 'static,
39{
40    // We assert that current registry has not terminated.
41    unsafe { spawn_broadcast_in(op, &Registry::current()) }
42}
43
44/// Provides context to a closure called by `broadcast`.
45pub struct BroadcastContext<'a> {
46    worker: &'a WorkerThread,
47
48    /// Make sure to prevent auto-traits like `Send` and `Sync`.
49    _marker: PhantomData<&'a mut dyn Fn()>,
50}
51
52impl<'a> BroadcastContext<'a> {
53    pub(super) fn with<R>(f: impl FnOnce(BroadcastContext<'_>) -> R) -> R {
54        let worker_thread = WorkerThread::current();
55        assert!(!worker_thread.is_null());
56        f(BroadcastContext {
57            worker: unsafe { &*worker_thread },
58            _marker: PhantomData,
59        })
60    }
61
62    /// Our index amongst the broadcast threads (ranges from `0..self.num_threads()`).
63    #[inline]
64    pub fn index(&self) -> usize {
65        self.worker.index()
66    }
67
68    /// The number of threads receiving the broadcast in the thread pool.
69    ///
70    /// # Future compatibility note
71    ///
72    /// Future versions of Rayon might vary the number of threads over time, but
73    /// this method will always return the number of threads which are actually
74    /// receiving your particular `broadcast` call.
75    #[inline]
76    pub fn num_threads(&self) -> usize {
77        self.worker.registry().num_threads()
78    }
79}
80
81impl<'a> fmt::Debug for BroadcastContext<'a> {
82    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
83        fmt.debug_struct("BroadcastContext")
84            .field("index", &self.index())
85            .field("num_threads", &self.num_threads())
86            .field("pool_id", &self.worker.registry().id())
87            .finish()
88    }
89}
90
91/// Execute `op` on every thread in the pool. It will be executed on each
92/// thread when they have nothing else to do locally, before they try to
93/// steal work from other threads. This function will not return until all
94/// threads have completed the `op`.
95///
96/// Unsafe because `registry` must not yet have terminated.
97pub(super) unsafe fn broadcast_in<OP, R>(op: OP, registry: &Arc<Registry>) -> Vec<R>
98where
99    OP: Fn(BroadcastContext<'_>) -> R + Sync,
100    R: Send,
101{
102    let f = move |injected: bool| {
103        debug_assert!(injected);
104        BroadcastContext::with(&op)
105    };
106
107    let n_threads = registry.num_threads();
108    let current_thread = WorkerThread::current().as_ref();
109    let latch = CountLatch::with_count(n_threads, current_thread);
110    let jobs: Vec<_> = (0..n_threads)
111        .map(|_| StackJob::new(&f, LatchRef::new(&latch)))
112        .collect();
113    let job_refs = jobs.iter().map(|job| job.as_job_ref());
114
115    registry.inject_broadcast(job_refs);
116
117    // Wait for all jobs to complete, then collect the results, maybe propagating a panic.
118    latch.wait(current_thread);
119    jobs.into_iter().map(|job| job.into_result()).collect()
120}
121
122/// Execute `op` on every thread in the pool. It will be executed on each
123/// thread when they have nothing else to do locally, before they try to
124/// steal work from other threads. This function returns immediately after
125/// injecting the jobs.
126///
127/// Unsafe because `registry` must not yet have terminated.
128pub(super) unsafe fn spawn_broadcast_in<OP>(op: OP, registry: &Arc<Registry>)
129where
130    OP: Fn(BroadcastContext<'_>) + Send + Sync + 'static,
131{
132    let job = ArcJob::new({
133        let registry = Arc::clone(registry);
134        move || {
135            registry.catch_unwind(|| BroadcastContext::with(&op));
136            registry.terminate(); // (*) permit registry to terminate now
137        }
138    });
139
140    let n_threads = registry.num_threads();
141    let job_refs = (0..n_threads).map(|_| {
142        // Ensure that registry cannot terminate until this job has executed
143        // on each thread. This ref is decremented at the (*) above.
144        registry.increment_terminate_count();
145
146        ArcJob::as_static_job_ref(&job)
147    });
148
149    registry.inject_broadcast(job_refs);
150}
rayon_core/broadcast/mod.rs

rayon_core/broadcast/
mod.rs
