Hubs, intervals and math

Portrait of Joaquín M López Muñoz Joaquín M López Muñoz · Apr 2, 2026

During Q1 2026, I’ve been working in the following areas:

boost::container::hub

boost::container::hub is a nearly drop-in replacement of C++26 std::hive sporting a simpler data structure and providing competitive performance with respect to the de facto reference implementation plf::hive. When I first read about std::hive, I couldn’t help thinking how complex the internal design of the container is, and wondered if something leaner could in fact be more effective. boost::container::hub critically relies on two realizations:

  • Identification of empty slots by way of std::countr_zero operations on a bitmask is extremely fast.
  • Modern allocators are very fast, too: boost::container::hub does many more allocations than plf::hive, but this doesn’t degrade its performance significantly (although it affects cache locality).

boost::container::hub is formally proposed for inclusion in Boost.Container and will be officially reviewed April 16-26. Ion Gaztañaga serves as the review manager.

using std::cpp 2026

I gave my talk “The Mathematical Mind of a C++ Programmer” at the using std::cpp 2026 conference taking place in Madrid during March 16-19. I had a lot of fun preparing the presentation and delivering the actual talk, and some interesting discussions were had around it. This is a subject I’ve been wanting to talk about for decades, so I’m somewhat relieved I finally got it over with this year. Always happy to discuss C++ and math, so if you have feedback or want to continue the conversation, please reach out to me.

Boost.Unordered

  • Written maintenance fixes PR#328, PR#335, PR#336, PR#337, PR#339, PR#344, PR#345. Some of these fixes are related to Node.js vulnerabilities in the Antora setup used for doc building: as the number of Boost libraries using Antora is bound to grow, maybe we should think of an automated way to get these vulnerabilities automatically fixed for the whole project.
  • Reviewed and merged PR#317, PR#332, PR#334, PR#341, PR#342. Many thanks to Sam Darwin, Braden Ganetsky and Andrey Semashev for their contributions.

Boost.Bimap

Merged PR#31 (std::initializer_list constructor) and provided testing and documentation for this new feature (PR#54). The original PR was silently sitting on the queue for more than four years and it was only when it was brought to my attention in a Reddit conversation that I got to take a look at it. Boost.Bimap needs an active mantainer, I guess I could become this person.

Boost.ICL

Recent changes in libc++ v22 code for associative container lookup have resulted in the breakage of Boost.ICL. My understanding is that the changes in libc++ are not standards conformant, and there’s an ongoing discussion on that; in the meantime, I wrote and proposed a PR to Boost.ICL that fixes the problem (pending acceptance).

Support to the community

  • I’ve been helping a bit with Mark Cooper’s very successful Boost Blueprint series on X.
  • Supporting the community as a member of the Fiscal Sponsorship Committee (FSC).

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