P2999 R3 Sender Algorithm Customization

[wg21bot]

P2999R0 Sender Algorithm Customization (Eric Niebler)

[inbal2l]

D2999R1 Sender Algorithm Customization (Eric Niebler)
Will be seen in Kona, Nov 2023 meeting

[inbal2l]

Library Evolution Telecon 2022-11-06

D2999R1: Sender Algorithm Customization

2023-11-06 Library Evolution Kona Minutes

Champion: Eric Niebler

Chair: Inbal Levi / Fabio Fracassi

Minute Taker: Ben Craig

Start: 2023-11-07

Summary

POLL: We want to add late customizations (as proposed by D2999R1)

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
9	10	0	0	1

Attendance: 27 + 7 = 34

# of Authors: 1

Author Position: SF

Outcome: Strong consensus in favor

SA: Worried about the increasing complexity, and how it will impact user adoption. Would like to see investigation on removing early customization first

POLL: We should explore getting rid of early customization (paper required)

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
5	9	7	2	0

Attendance: 27 + 7 = 34

# of Authors: 1

Author Position: N

Outcome: Consensus

WA: "If we just did this, we could make the whole thing simpler" around early customizations. We should just do that.

POLL: We generally approve on the customization mechanism presented in D2999R1

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
6	12	1	1	1

Attendance: 27+7 = 34

# of Authors: 1

Author Position: SF

Outcome: Consensus

SA: Would like to see investigation in higher granularity than domains

The proposed mechanism for CPs was supported by LEWG.

Requested additions:

• Examples of usability of the sender_of concept (and - possibly - alternative design)
• The author will consider the following names, and come back with either reasoning for the existing one (in the paper) or an alternative one. Refer to the following name for the utility currently called “is_sender”/”is_receiver”:
  • is_sender, is_receiver
  • sender_tag, receiver_tag
  • enable_sender, enable_receiver

Next Steps

During the next meeting we will take the following steps:

• Review: What are the expected outcomes in different use cases (different pipelines, mixing different domains) - require more examples
• Whether or not we require the existence of an early CP (the room seems to prefer a single late CP, need to poll)
• Poll on late CP
• Poll on moving back from std:: namespace (LWG to come back with reasoning - take the following poll: POLL: Revert the recommendation by LWG: get_env, empty_env, and env_of_t are moved into the std:: namespace.)
• Poll / approve by the room the sender_of concept names

[inbal2l]

D2999R2: Sender Algorithm Customization
Scheduled for LEWG in Kona 2023 (Thursday)

[inbal2l]

Library Evolution Telecon 2022-11-09

D2999R1: Sender Algorithm Customization

2023-11-09 Library Evolution Kona Minutes

Champion: Eric Niebler

Chair: Inbal Levi / Fabio Fracassi

Minute Taker: Ben Craig

Summary

POLL: Remove the sender_of concept (without prejudice, can be readded later, possibly with a different semantic)

SF	F	N	A	SA
7	8	4	0	1

Attendance: 22 + 4

# of Authors: 2

Authors’ position: SF SF

Outcome: Consensus in favour

SA: This removes functionality that is too useful. In case I want a different version, it helps to have this one in the standard.

Next Steps

The authors will remove the "sender_of" concept from this version (we would like to re-design the shape of the concept).

LEWG will spend additional time on this paper during the Kona meeting.

[ben-craig]

Library Evolution Telecon 2022-11-10

D2999R2: Sender Algorithm Customization

2023-11-10 Library Evolution Kona Minutes

Champion: Eric Niebler

Chair: Inbal Levi, Ben Craig

Minute Taker: Andreas Weis

Summary

POLL: Approve design of D2999R2 (Sender Algorithm Customization). (not a forwarding poll)

Strongly Favor	Weakly Favor	Neutral	Weakly Against	Strongly Against
9	12	2	0	0

Attendance: 27+5

# of Authors: 1

Author Position: SF

Outcome: Strong consensus in favor

Next Steps

The design was approved. The P paper should get back to LEWG to make sure the wording fits the design intent.
NOTE: This should be merged into P2300, not into the standard (no need for electronic poll)

[inbal2l]

2023-12-05 Library Evolution Telecon

P2999R2: Sender Algorithm Customization

2023-12-05 Library Evolution Telecon Minutes

Champion: Eric Niebler

Chair: Fabio Fracassi

Minute Taker: Ben Craig

Summary

The wording of the paper was reviewed (requires more time).
The topic of removing early customization was brought up, and as the Kona discussion suggested it requires more exploration (but shouldn't block the work on P2999) LEWG still asks for a paper for that (this was referred to and polled during Kona).

No polls were taken.

Next Steps

LEWG needs to continue reviewing the wording in P2999R2.

[inbal2l]

2023-12-12 Library Evolution Telecon

P2999R2: Sender Algorithm Customization

2023-12-12 Library Evolution Telecon Minutes

Champion: Eric Niebler

Chair: Fabio Fracassi

Minute Taker: Ben Craig

• Why should this utility go into the standard library? Needs to be used in the implementation of Sender algorithms
• Examples? Yes
• Discussion of prior art? yes
• Implementation experience? yes
  • Usage experience? yes
  • Deployment experience? no
• Performance considerations? yes
• Changes Library Evolution previously requested? yes
• Support in "std::format" and "hash" (if required)? n/a
• Feature test macro? not needed, will be integrated with P2300
• Freestanding? no change
• Wording? yes (in review)

Summary

The topic of removing early customization was brought up, and as the Kona discussion suggested it requires more exploration (but shouldn't block the work on P2999) LEWG still asks for a paper for that (this was referred to and polled during Kona).

The wording of the paper was reviewed:

• clarified the intent of the transform_sender API
• naming of transform_sender follows await_transform (because it has similar purpose)
• In the: Editor's note: To section §11.9.1 [exec.snd.concepts], after paragraph 4, add two new paragraphs as follows:
  Avoid using not yet standard features, make sure this can be implemented in current C++.
• Back out of the drive by fix on conjunction in [exec.schedule.from]
• In [exec.snd.transform] make sure that the mandates from [exec.???] are not lost.
• In [exec.when.all] §4 make the "unspecified" "unused" (or a note to that effect)

To be continued at [exec.start.detached] in R3 with the changes above incorporated.

No polls were taken.

The author will produce a new revision (R3) that incorporates the points mentioned. We will finish the review of [exec.start.detached], [exec.sync.wait] and [exec.execute].

Next Steps

• LEWG needs to continue reviewing the wording in P2999R2/3.
• Forwarding poll

[wg21bot]

P2999R1 Sender Algorithm Customization (Eric Niebler)

[wg21bot]

P2999R2 Sender Algorithm Customization (Eric Niebler)

[wg21bot]

P2999R3 Sender Algorithm Customization (Eric Niebler)

[FabioFracassi]

2023-12-19 Library Evolution Telecon

P2999R3: Sender Algorithm Customization

2023-12-13 Library Evolution Telecon Minutes

Champion: Eric Niebler

Chair: Fabio Fracassi

Minute Taker: Ben Craig

Summary

Short review of the remaining wording. No further changes were requested

POLL: Send "[P2999R3] Sender Algorithm Customization" to Library Working Group for C++26, to be confirmed by electronic polling.

SF	F	N	A	SA
3	5	2	0	1

SA: Complexity of S/R is getting too complex, the complexity was not discussed here.

Attendance: 20

# of Authors: 1

Author's Position: SF

Outcome: Consensus in favour

Next Steps

P2999R3 was forwarded to LWG (applied on P2300) to be confirmed with an electronic poll.

[inbal2l]

P2999R3 was added to LEWG 2023 December electronic poll paper (P3053R0)

[inbal2l]

P2999R3 was forwarded to LWG on LEWG 2023 December electronic poll (P3054R0)