std::execution::scheduler

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

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Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Execution Library

Execution concepts scheduler receiver receiver_of operation_state    sender sender_in sender_to Execution components Execution contexts run_loop Execution domains default_domain Forward progress guarantee forward_progress_guarantee Environments empty_env    get_env    env_of_t Queries std::stop_token_of_t std::get_stop_token std::get_allocator std::forwarding_query get_scheduler get_domain get_forward_progress_guarantee get_delegation_scheduler get_completion_scheduler Completion signatures completion_signatures completion_signatures_of_t transform_completion_signatures transform_completion_signatures_of    value_types_of_t error_types_of_t    tag_of_t sends_stopped    Sender adaptor closures sender_adaptor_closure Coroutine utility as_awaitable with_awaitable_senders

Core operations Operation state connect connect_result_t start Completion set_value set_error set_stopped Transformation transform_env transform_sender apply_sender Sender algorithms Sender factories just just_error just_stopped read_env schedule schedule_result_t Sender adaptors starts_on continues_on    on then upon_error upon_stopped let_value let_error let_stopped schedule_from when_all when_all_with_variant into_variant stopped_as_optional stopped_as_error bulk split Sender consumers this_thread::sync_wait this_thread::sync_wait_with_variant

 

Defined in header <execution>
template<class Sch>   concept scheduler =     std::derived_from<       typename std::remove_cvref_t<Sch>::scheduler_concept,       scheduler_t>     &&       /*queryable*/<Sch>     &&       requires(Sch&& sch)       {         { std::execution::schedule(std::forward<Sch>(sch) ) } -> std::execution::sender;         { auto(            std::execution::get_completion_scheduler< std::execution::set_value_t >(              std::execution::get_env(                std::execution::schedule(                  std::forward<Sch>(sch))))) }               -> std::same_as<std::remove_cvref_t<Sch>>;       }     &&       std::equality_comparable<std::remove_cvref_t<Sch>>     &&       std::copy_constructible<std::remove_cvref_t<Sch>>; };		(since C++26)

The concept scheduler is modeled by types that are schedulers, that is, lightweight handlers to execution resources such as thread pools that work with the C++ execution library.

Semantic requirements

Given a scheduler of type Sch and execution environment of type Env such that sender_in<schedule_result_t<Sch>, Env> is satisfied, then /*sender-in-of*/<schedule_result_t<Sch>, Env> is modeled.

The scheduler's copy constructor, destructor, equality comparison, or swap member functions must be non-throwing.

All of those member functions as well as the scheduler type's schedule function must be thread-safe.

Two schedulers are equal only if they represent the same execution resource.

For a given scheduler sch, the expression get_completion_scheduler<set_value_t>(get_env(schedule(sch))) compares equal to sch.

For a given scheduler sch, if the expression get_domain(sch) is well-formed, then the expression get_domain(get_env(schedule(sch))) is also well-formed and has the same type.

The destructor of a scheduler must not block pending completion of any receivers connected to the sender objects returned from schedule (the underlying resource may provide a separate API to wait for completion of submitted function objects)

Examples

simple wrapper for std::execution::run_loop

Run this code

#include <execution>
#include <thread>
 
class single_thread_context {
  std::execution::run_loop loop_;
  std::thread thread_;
 
public:
  single_thread_context()
    : loop_()
    , thread_([this] { loop_.run(); })
  {}
  single_thread_context(single_thread_context&&) = delete;
 
  ~single_thread_context() {
    loop_.finish();
    thread_.join();
  }
 
  auto get_scheduler() noexcept {
    return loop_.get_scheduler();
  }
 
  std::thread::id get_thread_id() const noexcept {
    return thread_.get_id();
  }
};
 
int main()
{
  // TODO
}

See also

execution::schedule (C++26)

prepares a task graph for execution on a given scheduler (customization point object)