cppdraft_translate/cppdraft/exec/sysctxrepl/psb.md

[exec.sysctxrepl.psb]

33 Execution control library [exec]

33.16 Namespace system_context_replaceability [exec.sysctxrepl]

33.16.3 Class parallel_scheduler_backend [exec.sysctxrepl.psb]

namespace std::execution::system_context_replaceability {struct parallel_scheduler_backend {virtual ~parallel_scheduler_backend() = default; virtual void schedule(receiver_proxy&, span) noexcept = 0; virtual void schedule_bulk_chunked(size_t, bulk_item_receiver_proxy&, span) noexcept = 0; virtual void schedule_bulk_unchunked(size_t, bulk_item_receiver_proxy&, span) noexcept = 0; };}

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virtual void schedule(receiver_proxy& r, span<byte> s) noexcept = 0;

1

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Preconditions: The ends of the lifetimes of *this, the object referred to by r, and any storage referenced by s all happen after the beginning of the evaluation of the call to set_value, set_error, or set_done on r (see below).

2

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Effects: A derived class shall implement this function such that:

• (2.1)

  One of the following expressions is evaluated:

  • (2.1.1)

r.set_value(), if no error occurs, and the work is successful;

• (2.1.2)

r.set_error(eptr), if an error occurs, where eptr is an object of type exception_ptr;

• (2.1.3)

r.set_stopped(), if the work is canceled.

• (2.2)

  Any call to r.set_value() happens on an execution agent of the execution context represented by *this.

3

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Remarks: The storage referenced by s may be used by *this as temporary storage for the duration of the operation launched by this call.

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virtual void schedule_bulk_chunked(size_t n, bulk_item_receiver_proxy& r, span<byte> s) noexcept = 0;

4

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Preconditions: The ends of the lifetimes of *this, the object referred to by r, and any storage referenced by s all happen after the beginning of the evaluation of one of the expressions below.

5

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Effects: A derived class shall implement this function such that:

• (5.1)

  Eventually, one of the following expressions is evaluated:

  • (5.1.1)

r.set_value(), if no error occurs, and the work is successful;

• (5.1.2)

r.set_error(eptr), if an error occurs, where eptr is an object of type exception_ptr;

• (5.1.3)

r.set_stopped(), if the work is canceled.

• (5.2)

  If r.execute(b, e) is called, then b and e are in the range [0, n] andb < e.

• (5.3)

  For each i in [0, n), there is at most one call to r.execute(b, e) such that i is in the range [b, e).

• (5.4)

  If r.set_value() is called, then for each i in [0, n), there is exactly one call to r.execute(b, e) such that i is in the range [b, e).

• (5.5)

  All calls to execute on r happen before the call to either set_value, set_error, or set_stopped on r.

• (5.6)

  All calls to execute and set_value on r are made on execution agents of the execution context represented by *this.

6

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Remarks: The storage referenced by s may be used by *this as temporary storage for the duration of the operation launched by this call.

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virtual void schedule_bulk_unchunked(size_t n, bulk_item_receiver_proxy& r, span<byte> s) noexcept = 0;

7

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Preconditions: The ends of the lifetimes of *this, the object referred to by r, and any storage referenced by s all happen after the beginning of the evaluation of one of the expressions below.

8

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Effects: A derived class shall implement this function such that:

• (8.1)

  Eventually, one of the following expressions is evaluated:

  • (8.1.1)

r.set_value(), if no error occurs, and the work is successful;

• (8.1.2)

r.set_error(eptr), if an error occurs, where eptr is an object of type exception_ptr;

• (8.1.3)

r.set_stopped(), if the work is canceled.

• (8.2)

  If r.execute(b, e) is called, then b is in the range [0, n) ande is equal to b + 1. For each i in [0, n), there is at most one call to r.execute(i, i + 1).

• (8.3)

  If r.set_value() is called, then for each i in [0, n), there is exactly one call to r.execute(i, i + 1).

• (8.4)

  All calls to execute on r happen before the call to either set_value, set_error, or set_stopped on r.

• (8.5)

  All calls to execute and set_value on r are made on execution agents of the execution context represented by *this.

9

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Remarks: The storage referenced by s may be used by *this as temporary storage for the duration of the operation launched by this call.