Hi all, from the notes to the Apr 10th meeting now that all papers have been published  in the April mailing. We wishes to take a vote on these papers to exit SG19 to head to LEWG. Please prepare accordingly. Thank you.

The group reviewed updates to five papers, focusing on descriptors in graph algorithms, which reduce interface complexity and improve performance. They also discussed the implementation of accumulator objects for statistical functions, considering compile-time configuration to avoid runtime overhead. The need for further experimentation and potential delay of the accumulator to a second paper was suggested. The meeting concluded with plans to publish updated papers by April 15 for a potential vote in May.

Action Items


Michael Wong is inviting you to a scheduled Zoom meeting.

Topic: SG19 monthly
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Agenda:

1. Opening and introductions

The ISO Code of conduct:
https://www.iso.org/files/live/sites/isoorg/files/store/en/PUB100397.pdf

IEC Code of Conduct:

https://www.iec.ch/basecamp/iec-code-conduct-technical-work

ISO patent policy.

https://isotc.iso.org/livelink/livelink/fetch/2000/2122/3770791/Common_Policy.htm?nodeid=6344764&vernum=-2

The WG21 Practices and Procedures and Code of Conduct:
https://isocpp.org/std/standing-documents/sd-4-wg21-practices-and-procedures

1.1 Roll call of participants

1.2 Adopt agenda

1.3 Approve minutes from previous meeting, and approve publishing
 previously approved minutes to ISOCPP.org

1.4 Action items from previous meetings

2. Main issues (125 min)

2.1 General logistics




* Jan 9, 2025 02:00 PM ET: Cancelled
* Feb 13, 2025 02:00 PM ET: Hagenberg F2F; Cancelled
* Mar 13, 2025 02:00 PM ET: Graph
* Apr 10, 2025 02:00 PM ET: Stats
* May 8, 2025 02:00 PM ET: Graph
* June 12, 2025 02:00 PM ET: Stats
* July 10, 2025 02:00 PM ET: Graphs
* Aug 14, 2025 02:00 PM ET: Stats
* Sep 11, 2025 02:00 PM ET: Graph, CPPCON
* Oct 9, 2025 02:00 PM ET: Stats
* Nov 13, 2025 02:00 PM ET: Graph
* Dec 11, 2025 02:00 PM ET: Stats


ISO meeting status

future C++ Std meetings

2.2 Paper reviews

For graph, we have a new draft of P3337 Comparison paper that compares the
library in performance against boost::graph and NWGraph.

If Andrew is able to attend, he should be able to review the changes he's
made to P3126 and P3127.


P3495 from Oliver/Mark

>From Phil: There are updates to the P3126 Overview and P3127 Background and
Terminology papers for the Graph Library. They haven’t been published yet,
but it would be helpful to get input on them before they’re published.



Since the changes are a response to Oliver’s concerns, I think Oliver and
Andrew would need to attend to make it useful to have a session for the
Graph Library. Unless they want to do that, I think we can send draft
versions to the reflector, unless there’s a better idea.


Review BSI Graph feedback:
As Oliver (Rosten) said "The basic premise is important, and it would be
fantastic to have support for graphs in the standard."

The main items identified were:
Oliver:
- This paper is long and incomplete, it has lots of details which I think
to be irrelevant, however things that are definitely relevant are missing
from the paper - for example definition of graph - since people have
different ideas. We need to add a mathematical perspective to the paper.

- The structure of the paper completely changed in the new revision, so now
it’s hard to understand what and why they have done

- Another missing part is discussion of graph invariants

Tom (Deakin): There’s a big missing part in “Prior art” part, GraphBLAS (
https://graphblas.org) eminently.

Some other things to add:

1. The electrical circuit example needs more explanation, and I think this
will highlight some deep issues around representing things which are
seemingly trivially graphs, as graphs in practice. In what sense is a
bog-standard resistor directed? I assume the reason that the graph is
directed is because current has a sign and in an undirected graph it
becomes ambiguous which way the current is flowing (also you may want
components like diodes). But the directed representation also has issues:
"can current flow from 'Vdd' to 'n0'?" should be immediately answerable
from the properties of Vdd and its edges. There are other ways to represent
an electrical circuit. One is as a directed graph but with incident edges
recorded - but iiuc, this is excluded from the latest version of the paper.
Alternatively, one could have a mathematical object, the name of which I
actually don't know: it looks like an undirected graph, but where each
partial edge has additional, unique, end-point data, as well as the common
weight. Things like this are the reason why I think we need a broader group
to look at this proposal (i.e. beyond SG19) and if we possibly can we
should involve someone from the mathematics community. Otherwise there's a
real danger we end up missing important insights.

2. My comment about the structure of the paper changing was a reference to
previous comparisons with boost::graph. I'm sure these were in an earlier
version, or am I misremembering? Either way, it would be very helpful to
have a proper discussion of e.g. the move away from visitors.

3. Re. the definition of a graph, there needs to be a proper discussion
about whether the paper's definition of graph is what some authors call a
multigraph and whether it does/does not include loops. These things are
mentioned, in passing, when introducing algorithms, but terminology needs
to be properly established.

4. I think we're trying to do too much in one go in this paper. I think a
great first step would be to build on mdspan and try to standardize (or at
least understand) what might reasonably be called an unstructured span.
This could be represented as a vector of vectors or as a vector with some
auxiliary storage indicating where the partitions fall. The point is that
an unstructured span, with the right invariants, is an adjacency list. If
we can understand unstructured span and its desirable api, I think this
will be incredibly valuable guidance for what a standardized graph
container might look like.

5. IIUC, this paper excludes pure connectivity graphs. These are incredibly
helpful and, if I've understood correctly that they are not supported,
would be a major omission. Another good reason, imo, to start with
unstructured span!

6. I'm not convinced by the load api. We don't have a load api for vector
etc. Moreover, would it not be preferable to have appropriate constructors?


2.2.1: ML topics

2.2.1.1 Graph Proposal Phil Ratsloff et al

Latest paper:

Here’s a link to the paper (different than the previous paper reviewed).
There are some additional updates I’m planning on making before the meeting.

https://docs.google.com/document/d/1OpH-xxRri7tJTtJJIZTYmSHkkrZJkdBwm9zJ7LqolfQ/edit?usp=sharing




P1709R3:
https://docs.google.com/document/d/1kLHhbSTX7j0tPeTYECQFSNx3R35Mu3xO5_dyYdRy4dM/edit?usp=sharing

https://docs.google.com/document/d/1QkfDzGyfNQKs86y053M0YHOLP6frzhTJqzg1Ug_vkkE/edit?usp=sharing

<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2119r0.html>

<
https://docs.google.com/document/d/175wIm8o4BNGti0WLq8U6uZORegKVjmnpfc-_E8PoGS0/edit?ts=5fff27cd#heading=h.9ogkehmdmtel
*>*

Array copy semantics:
array copy-semantics paper P1997 "Relaxing Restrictions on Arrays",
https://wg21.link/p1997

Stats feedback:

P2376R0
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2376r0.pdf>
Comments
on Simple Statistical Functions (p1708r4): Contracts, Exceptions and
Special cases Johan Lundberg

2.2.1.2 Reinforcement Learning Larry Lewis Jorge Silva

Reinforcement Learning proposal:

2.2.1.3 Differential Calculus:

https://docs.google.com/document/d/175wIm8o4BNGti0WLq8U6uZORegKVjmnpfc-_E8PoGS0/edit?ts=5fff27cd#heading=h.9ogkehmdmtel

2.2.1.4: Stats paper

P2681R0
<https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2681r0.pdf> More
Stats Functions Richard Dosselmann, Michael Wong
Current github

https://github.com/cplusplus/papers/issues/475

https://github.com/cplusplus/papers/issues/979

Stats review Richard Dosselman et al

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p1708r4.pdf

Feedback from Johan Lundberg and Oleksandr Korval

https://isocpp.org/files/papers/D2376R0.pdf

P1708R3: Math proposal for Machine Learning: 3rd review

PXXXX: combinatorics: 1st Review

*> std.org/jtc1/sc22/wg21/docs/papers/2020/p1708r2
<http://std.org/jtc1/sc22/wg21/docs/papers/2020/p1708r2>*
*> above is the stats paper that was reviewed in Prague*
*> http://wiki.edg.com/bin/view/Wg21prague/P1708R2SG19
<http://wiki.edg.com/bin/view/Wg21prague/P1708R2SG19>*
*>*
*> Review Jolanta Polish feedback.*
*> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2119r0.html
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2119r0.html>*


2.2.1.4: Matrix paper

2.2.3 any other proposal for reviews?

2.3 Other Papers and proposals

P1416R1: SG19 - Linear Algebra for Data Science and Machine Learning
https://docs.google.com/document/d/1IKUNiUhBgRURW-UkspK7fAAyIhfXuMxjk7xKikK4Yp8/edit#heading=h.tj9hitg7dbtr

P1415: Machine Learning Layered list
https://docs.google.com/document/d/1elNFdIXWoetbxjO1OKol_Wj8fyi4Z4hogfj5tLVSj64/edit#heading=h.tj9hitg7dbtr

2.2.2 SG14 Linear Algebra progress:
Different layers of proposal
https://docs.google.com/document/d/1poXfr7mUPovJC9ZQ5SDVM_1Nb6oYAXlK_d0ljdUAtSQ/edit

2.5 Future F2F meetings:

2.6 future C++ Standard meetings:
https://isocpp.org/std/meetings-and-participation/upcoming-meetings

None

3. Any other business

New reflector

http://lists.isocpp.org/mailman/listinfo.cgi/sg19

Old Reflector
https://groups.google.com/a/isocpp.org/forum/#!newtopic/sg19
<https://groups.google.com/a/isocpp.org/forum/?fromgroups=#!forum/sg14>

Code and proposal Staging area

4. Review

4.1 Review and approve resolutions and issues [e.g., changes to SG's
working draft]

4.2 Review action items (5 min)

5. Closing process

5.1 Establish next agenda


5.2 Future meeting
* Jan 9, 2025 02:00 PM ET: Cancelled
* Feb 13, 2025 02:00 PM ET: Hagenberg F2F; Cancelled
* Mar 13, 2025 02:00 PM ET: Graph 
* Apr 10, 2025 02:00 PM ET: Stats
* May 8, 2025 02:00 PM ET: Graph
* June 12, 2025 02:00 PM ET: Stats
* July 10, 2025 02:00 PM ET: Graphs
* Aug 14, 2025 02:00 PM ET: Stats
* Sep 11, 2025 02:00 PM ET: Graph, CPPCON
* Oct 9, 2025 02:00 PM ET: Stats
* Nov 13, 2025 02:00 PM ET: Graph
* Dec 11, 2025 02:00 PM ET: Stats