On Wed, Apr 8, 2026 at 5:31 PM Phil Ratzloff via SG19 <sg19_at_[hidden]>
wrote:

> Hi all,
> there will be an SG19 meeting at 2 PM ET on Thursday, April 9.
> (Sorry for the late notice.)
>
> Phil Ratzloff is inviting you to a scheduled Zoom meeting.
>
> Topic: SG19 Machine Learning Monthly Meeting
> Time: Feb 12, 2026 02:00 PM Eastern Time (US and Canada)
> Every month on the Second Thu
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Michael W, Phil R, Pete I, Scott M, Chaanka

The meeting discussed the evolution of the forward index and its impact on
simplifying code, including the addition of sparse vertex IDs and
bi-directional graph support. The reference implementation now includes a
full suite of tests, totaling 80,000 lines. Algorithm changes were
highlighted, such as the introduction of vertex property maps and visitor
patterns for shortest paths and depth-first search. The team debated the
acceptability of algorithms that allocate memory internally and the need
for parallel implementations. The discussion also covered the integration
of the statistics library with existing libraries and the potential impact
of the units library on future developments.Action Items

   - PR Email the LEWG reflector to ask whether graph algorithms allocating
   internal workspace is acceptable and introduce the requestor on their behalf
   - PR Contact L E WG (or relevant reflector) about
   allocation/space-complexity policy for algorithms and present the
   trade-offs to de-risk the proposal
   - @Michael Wong - Mention the statistics/graph library to the C++
   Alliance / Beeman project maintainers and inquire about hosting or review
   options
   - @Michael Wong - Provide the vote results and information on accessing
   the ISO CPP wiki (voting records) to the statistics paper author
   - @Michael Wong - Connect the statistics proposal author with the
   units-library author (Matus) and evaluate how the units library impacts the
   statistics proposal; report back
   - Phil take responsibility for the SG-19 meeting on May 14 (cover the
   meeting in the presenter's absence)
   - Richard Cite the committee vote results in the next version of the
   statistics paper (include voting evidence in the paper)
   - MW Contact the boost maintainers for the graph library to request
   review and discuss hosting or collaboration

OutlineForward Iterators and Additional Features

   - PR discusses the introduction of forward iterators and how it
   simplifies the code by reducing the number of functions needed.
   - The addition of sparse vertex IDs allows for non-interval vertex IDs,
   which can be useful in certain use cases.
   - View chaining using the pipe operator is introduced to support
   bi-directional graphs, with additional functions added to support this.
   - The dynamic graph is extended to support bi-directional graphs, which
   is not part of the proposal but is included for testing purposes.

Reorganization of Namespaces and Testing

   - PR explains the reorganization of namespaces to separate adjacency
   lists and edge lists, ensuring they are true peers.
   - The testing suite has been expanded to include a full suite of tests,
   now totaling around 80,000 lines, providing more confidence in the
   implementation.
   - The previous presentation and proposals are reviewed, with a focus on
   the algorithms and areas that have changed.
   - Common algorithm definitions are discussed, including edge weight
   concepts and the introduction of the vertex descriptor and ordered vertex
   edges.

Vertex Property Map and Distance Function

   - The vertex property map is introduced to store values like distance or
   predecessor, which can be stored in a vector or unordered map.
   - The distance function and predecessor function are discussed, with
   changes to accommodate storing these values in either an external container
   or as properties on the vertex itself.
   - The concept of vertex visitors is introduced, which can be called on
   different events during the algorithm's execution.
   - The algorithms for breadth-first search and depth-first search are
   updated to support both random access and forward range types of vertex
   containers.

Discussion on Allocation and Space Complexity

   - The discussion shifts to the allocation of internal data structures
   used by algorithms, such as stacks or queues, and the importance of
   considering space complexity.
   - Scott raises a question about whether algorithms that allocate their
   own internal workspace will be accepted by the library evolution working
   group (LEWG).
   - Michael Wong suggests framing allocation as an observable, bounded,
   and optional user-supplied buffer to address space efficiency concerns.
   - The importance of documenting space complexity and offering overloads
   that take a caller-provided working buffer is emphasized.

Feedback on Graph Algorithms and Future Steps

   - The discussion includes feedback on the Dijkstra shortest paths
   algorithm, with changes to the edge descriptor to improve performance.
   - The use of visitors in algorithms like shortest paths, breadth-first
   search, and depth-first search is highlighted.
   - The need for early engagement with LEWG to address questions about
   allocation and space complexity is emphasized.
   - The meeting concludes with a discussion on the next steps for the
   graph library, including the need to reduce placeholder sections and
   complete the paper.