New Boost library proposal and a talk on how to make C++ ranges faster

By Joaquín M López Muñoz on
Apr 8, 2025

During Q1 2025, I’ve been working in the following areas:

Candidate Boost Bloom Library

During the entire quarter I’ve been working on a Boost proposal around Bloom filters:

Class template boost::bloom::filter can be configured to implement a classical Bloom filter as well as variations discussed in the literature such as block filters, multiblock filters, and more.

#include <boost/bloom/filter.hpp>
#include <cassert>
#include <string>

int main()
{
  // Bloom filter of strings with 5 bits set per insertion
  using filter = boost::bloom::filter<std::string, 5>;

  // create filter with a capacity of 1'000'000 **bits**
  filter f(1'000'000);

  // insert elements (they can't be erased, Bloom filters are insert-only)
  f.insert("hello");
  f.insert("Boost");
  //...

  // elements inserted are always correctly checked as such
  assert(f.may_contain("hello") == true);

  // elements not inserted may incorrectly be identified as such with a
  // false positive rate (FPR) which is a function of the array capacity,
  // the number of bits set per element and generally how the boost::bloom::filter
  // was specified
  if(f.may_contain("bye")) { // likely false
    //...
  }
}

The library is ready for official review, which I plan to ask for in April. Chris Mazakas is helping with a very useful vcpkg registry so that future reviewers can download and install candidate Boost.Bloom and dependencies with minimal hassle via vcpkg.

Presentation at using std::cpp 2025

I prepared and presented the talk “Push is Faster” at the using std::cpp 2025 conference in Madrid, March 19-21:

https://github.com/joaquintides/usingstdcpp2025

(The video of the talk will be publicly available in a few weeks.) We discussed push and pull paradigms for sequential data processing, why C++ ranges are not as fast as they could be, and an alternative design based on so-called transrangers. If feedback is positive, I may eventually grow the transrangers proof-of-concept library into a full-fledged proposal for Boost.

Boost.Unordered

  • Reviewed PR#299 from Chris Mazakas, a complete migration of Boost.Unordered documentation to Antora. The new docs are multi-page and generally much nicer looking. Great work, Chris!
  • Retouched some aspects of the new Antora docs (PR#303) and filed some pending issues (#304).

Boost promotion

  • Posted a tweet publicizing Rubén Pérez’s work on module support for Boost.
  • Provided support to Rob Beeston for the creation of a Boost.Unordered poster to be displayed at the upcoming WG21 meeting in Sofia, Bulgaria.

Support to the community

  • I’ve pre-reviewed Jean-Louis Leroy’s Boost.OpenMethod proposal.
  • Supporting the community as a member of the Fiscal Sponsorhip Committee (FSC). Asset transfer from the Boost Foundation to the C++ Alliance is still being negotiated, I hope all pending issues can be cleared up soon.

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