Domain(3)

NAME
Domain - Domains.

Module
Module Domain

Documentation

Module Domain
 : sig end

Domains.

See 'Parallel programming' chapter in the manual.

Since 5.0

Alert unstable. The Domain interface may change in incompatible ways in the future.

type !'a t

A domain of type 'a t runs independently, eventually producing a result of type 'a, or an exception

val spawn : (unit -> 'a) -> 'a t

spawn f creates a new domain that runs in parallel with the current domain.

Raises Failure if the program has insufficient resources to create another domain.

val join : 'a t -> 'a

join d blocks until domain d runs to completion. If d results in a value, then that is returned by join d . If d raises an uncaught exception, then that is re-raised by join d .

If the domain has created any systhreads (via Thread.create ), then it tries to join those systhreads (same as calling Thread.join ) before returning.

type id = private int

Domains have unique integer identifiers

val get_id : 'a t -> id

get_id d returns the identifier of the domain d

val self : unit -> id

self () is the identifier of the currently running domain

val before_first_spawn : (unit -> unit) -> unit

before_first_spawn f registers f to be called before the first domain is spawned by the program. The functions registered with before_first_spawn are called on the main (initial) domain. The functions registered with before_first_spawn are called in 'first in, first out' order: the oldest function added with before_first_spawn is called first.

Raises Invalid_argument if the program has already spawned a domain.

val at_exit : (unit -> unit) -> unit

at_exit f registers f to be called when the current domain exits. Note that at_exit callbacks are domain-local and only apply to the calling domain. The registered functions are called in 'last in, first out' order: the function most recently added with at_exit is called first. An example:

    let temp_file_key = Domain.DLS.new_key (fun _ ->
      let tmp = snd (Filename.open_temp_file "" "") in
      Domain.at_exit (fun () -> close_out_noerr tmp);
      tmp)

The snippet above creates a key that when retrieved for the first time will open a temporary file and register an at_exit callback to close it, thus guaranteeing the descriptor is not leaked in case the current domain exits.

val cpu_relax : unit -> unit

If busy-waiting, calling cpu_relax () between iterations will improve performance on some CPU architectures

val is_main_domain : unit -> bool

is_main_domain () returns true if called from the initial domain.

val count : unit -> int

The number of domains that have been spawned (including the initial domain) and have not yet terminated.

Since 5.5

val recommended_domain_count : unit -> int

The recommended maximum number of domains which should be running simultaneously (including domains already running).

The value returned is at least 1 .

val self_index : unit -> int

The index of the current domain. It is an integer unique among currently-running domains, in the interval 0; N-1 where N is the peak number of domains running simultaneously so far.

The index of a terminated domain may be reused for a new domain. Use (Domain.self () :> int) instead for an identifier unique among all domains ever created by the program.

Since 5.3

module DLS : sig end