Struct rayon::ThreadPoolBuilder

pub struct ThreadPoolBuilder { /* fields omitted */ }

Used to create a new ThreadPool or to configure the global rayon thread pool.

Creating a ThreadPool

The following creates a thread pool with 22 threads.

let pool = rayon::ThreadPoolBuilder::new().num_threads(22).build().unwrap();

To instead configure the global thread pool, use build_global():

rayon::ThreadPoolBuilder::new().num_threads(22).build_global().unwrap();

Methods

impl ThreadPoolBuilder

pub fn new() -> ThreadPoolBuilder

Creates and returns a valid rayon thread pool builder, but does not initialize it.

pub fn build(self) -> Result<ThreadPool, ThreadPoolBuildError>

Create a new ThreadPool initialized using this configuration.

pub fn build_global(self) -> Result<(), ThreadPoolBuildError>

Initializes the global thread pool. This initialization is optional. If you do not call this function, the thread pool will be automatically initialized with the default configuration. Calling build_global is not recommended, except in two scenarios:

• You wish to change the default configuration.
• You are running a benchmark, in which case initializing may yield slightly more consistent results, since the worker threads will already be ready to go even in the first iteration. But this cost is minimal.

Initialization of the global thread pool happens exactly once. Once started, the configuration cannot be changed. Therefore, if you call build_global a second time, it will return an error. An Ok result indicates that this is the first initialization of the thread pool.

pub fn thread_name<F>(self, closure: F) -> ThreadPoolBuilder where
    F: FnMut(usize) -> String + 'static, 

Set a closure which takes a thread index and returns the thread's name.

pub fn num_threads(self, num_threads: usize) -> ThreadPoolBuilder

Set the number of threads to be used in the rayon threadpool.

If you specify a non-zero number of threads using this function, then the resulting thread-pools are guaranteed to start at most this number of threads.

If num_threads is 0, or you do not call this function, then the Rayon runtime will select the number of threads automatically. At present, this is based on the RAYON_NUM_THREADS environment variable (if set), or the number of logical CPUs (otherwise). In the future, however, the default behavior may change to dynamically add or remove threads as needed.

Future compatibility warning: Given the default behavior may change in the future, if you wish to rely on a fixed number of threads, you should use this function to specify that number. To reproduce the current default behavior, you may wish to use the num_cpus crate to query the number of CPUs dynamically.

Old environment variable: RAYON_NUM_THREADS is a one-to-one replacement of the now deprecated RAYON_RS_NUM_CPUS environment variable. If both variables are specified, RAYON_NUM_THREADS will be prefered.

pub fn panic_handler<H>(self, panic_handler: H) -> ThreadPoolBuilder where
    H: Fn(Box<Any + 'static + Send>) + Send + Sync + 'static, 

Normally, whenever Rayon catches a panic, it tries to propagate it to someplace sensible, to try and reflect the semantics of sequential execution. But in some cases, particularly with the spawn() APIs, there is no obvious place where we should propagate the panic to. In that case, this panic handler is invoked.

If no panic handler is set, the default is to abort the process, under the principle that panics should not go unobserved.

If the panic handler itself panics, this will abort the process. To prevent this, wrap the body of your panic handler in a call to std::panic::catch_unwind().

pub fn stack_size(self, stack_size: usize) -> ThreadPoolBuilder

Set the stack size of the worker threads

pub fn breadth_first(self) -> ThreadPoolBuilder

Suggest to worker threads that they execute spawned jobs in a "breadth-first" fashion. Typically, when a worker thread is idle or blocked, it will attempt to execute the job from the top of its local deque of work (i.e., the job most recently spawned). If this flag is set to true, however, workers will prefer to execute in a breadth-first fashion -- that is, they will search for jobs at the bottom of their local deque. (At present, workers always steal from the bottom of other worker's deques, regardless of the setting of this flag.)

If you think of the tasks as a tree, where a parent task spawns its children in the tree, then this flag loosely corresponds to doing a breadth-first traversal of the tree, whereas the default would be to do a depth-first traversal.

Note that this is an "execution hint". Rayon's task execution is highly dynamic and the precise order in which independent tasks are executed is not intended to be guaranteed.

pub fn start_handler<H>(self, start_handler: H) -> ThreadPoolBuilder where
    H: Fn(usize) + Send + Sync + 'static, 

Set a callback to be invoked on thread start.

The closure is passed the index of the thread on which it is invoked. Note that this same closure may be invoked multiple times in parallel. If this closure panics, the panic will be passed to the panic handler. If that handler returns, then startup will continue normally.

pub fn exit_handler<H>(self, exit_handler: H) -> ThreadPoolBuilder where
    H: Fn(usize) + Send + Sync + 'static, 

Set a callback to be invoked on thread exit.

The closure is passed the index of the thread on which it is invoked. Note that this same closure may be invoked multiple times in parallel. If this closure panics, the panic will be passed to the panic handler. If that handler returns, then the thread will exit normally.

Trait Implementations

impl Default for ThreadPoolBuilder

fn default() -> ThreadPoolBuilder

Returns the "default value" for a type.

impl Debug for ThreadPoolBuilder

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.