Struct rustc_rayon_core::ThreadPool [−][src]
pub struct ThreadPool { /* fields omitted */ }Expand description
Represents a user created thread-pool.
Use a ThreadPoolBuilder to specify the number and/or names of threads
in the pool. After calling ThreadPoolBuilder::build(), you can then
execute functions explicitly within this ThreadPool using
ThreadPool::install(). By contrast, top level rayon functions
(like join()) will execute implicitly within the current thread-pool.
Creating a ThreadPool
let pool = rayon::ThreadPoolBuilder::new().num_threads(8).build().unwrap();install() executes a closure in one of the ThreadPool’s
threads. In addition, any other rayon operations called inside of install() will also
execute in the context of the ThreadPool.
When the ThreadPool is dropped, that’s a signal for the threads it manages to terminate,
they will complete executing any remaining work that you have spawned, and automatically
terminate.
Implementations
👎 Deprecated: Use ThreadPoolBuilder::build
Use ThreadPoolBuilder::build
Deprecated in favor of ThreadPoolBuilder::build.
Executes op within the threadpool. Any attempts to use
join, scope, or parallel iterators will then operate
within that threadpool.
Warning: thread-local data
Because op is executing within the Rayon thread-pool,
thread-local data from the current thread will not be
accessible.
Panics
If op should panic, that panic will be propagated.
Using install()
fn main() {
let pool = rayon::ThreadPoolBuilder::new().num_threads(8).build().unwrap();
let n = pool.install(|| fib(20));
println!("{}", n);
}
fn fib(n: usize) -> usize {
if n == 0 || n == 1 {
return n;
}
let (a, b) = rayon::join(|| fib(n - 1), || fib(n - 2)); // runs inside of `pool`
return a + b;
}Returns the (current) number of threads in the thread pool.
Future compatibility note
Note that unless this thread-pool was created with a
ThreadPoolBuilder that specifies the number of threads,
then this number may vary over time in future versions (see the
num_threads() method for details).
If called from a Rayon worker thread in this thread-pool,
returns the index of that thread; if not called from a Rayon
thread, or called from a Rayon thread that belongs to a
different thread-pool, returns None.
The index for a given thread will not change over the thread’s lifetime. However, multiple threads may share the same index if they are in distinct thread-pools.
Future compatibility note
Currently, every thread-pool (including the global
thread-pool) has a fixed number of threads, but this may
change in future Rayon versions (see the num_threads() method
for details). In that case, the index for a
thread would not change during its lifetime, but thread
indices may wind up being reused if threads are terminated and
restarted.
Returns true if the current worker thread currently has “local tasks” pending. This can be useful as part of a heuristic for deciding whether to spawn a new task or execute code on the current thread, particularly in breadth-first schedulers. However, keep in mind that this is an inherently racy check, as other worker threads may be actively “stealing” tasks from our local deque.
Background: Rayon’s uses a work-stealing scheduler. The
key idea is that each thread has its own deque of
tasks. Whenever a new task is spawned – whether through
join(), Scope::spawn(), or some other means – that new
task is pushed onto the thread’s local deque. Worker threads
have a preference for executing their own tasks; if however
they run out of tasks, they will go try to “steal” tasks from
other threads. This function therefore has an inherent race
with other active worker threads, which may be removing items
from the local deque.
Execute oper_a and oper_b in the thread-pool and return
the results. Equivalent to self.install(|| join(oper_a, oper_b)).
Creates a scope that executes within this thread-pool.
Equivalent to self.install(|| scope(...)).
See also: the scope() function.
Creates a scope that executes within this thread-pool.
Spawns from the same thread are prioritized in relative FIFO order.
Equivalent to self.install(|| scope_fifo(...)).
See also: the scope_fifo() function.
Spawns an asynchronous task in this thread-pool. This task will
run in the implicit, global scope, which means that it may outlast
the current stack frame – therefore, it cannot capture any references
onto the stack (you will likely need a move closure).
See also: the spawn() function defined on scopes.
Spawns an asynchronous task in this thread-pool. This task will
run in the implicit, global scope, which means that it may outlast
the current stack frame – therefore, it cannot capture any references
onto the stack (you will likely need a move closure).
See also: the spawn_fifo() function defined on scopes.