std::execution::scheduler

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.

[edit] 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)

[edit] Examples

#include <execution>
#include <iostream>
#include <thread>
 
class single_thread_context
{
 std::execution::run_loop loop_{};
 std::jthread thread_;
 
public:
 single_thread_context()
 : thread_([this] { loop_.run(); })
 {}
 single_thread_context(single_thread_context&&) = delete;
 
 ~single_thread_context()
 {
 loop_.finish();
 }
 
 std::execution::scheduler auto get_scheduler() noexcept
 {
 return loop_.get_scheduler();
 }
};
 
int main()
{
 single_thread_context ctx;
 
 std::execution::sender auto snd =
 std::execution::schedule(ctx.get_scheduler())
 | std::execution::then([]
 {
 std::cout << "Hello world! Have an int.\n";
 return 015;
 })
 | std::execution::then([](int arg) { return arg + 42; });
 
 auto [i] = std::this_thread::sync_wait(snd).value();
 
 std::cout << "Back in the main thread, result is " << i << '\n';
}

Hello world! Have an int.
Back in the main thread, result is 55

[edit] See also

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