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[openmethod] Joaquin's syntax suggestion
by Jean-Louis Leroy 25 May '25

25 May '25

During the review, Joaquin suggested changing the syntax for declaring and overriding methods, from: BOOST_OPENMETHOD(poke, (virtual_ptr<Animal>, std::ostream&), void); BOOST_OPENMETHOD_OVERRIDE( poke, (virtual_ptr<Bulldog> dog, std::ostream& os), void) { ... } to: BOOST_OPENMETHOD(poke, void(virtual_ptr<Animal>, std::ostream&)); BOOST_OPENMETHOD_OVERRIDE( poke, void(virtual_ptr<Bulldog> dog, std::ostream& os)) { ... } The difficulty with this is that the macros generate several constructs using the method name, formal parameter list and return type. Steven suggested a trick to implement a similar syntax, using trailing return types: BOOST_OPENMETHOD(poke, (virtual_ptr<Animal>, std::ostream&)->void); BOOST_OPENMETHOD_OVERRIDE( poke, (virtual_ptr<Bulldog> dog, std::ostream& os)->void) { ... } but I am not 100% sure if he actually _supports_ the change. @Steven, do you? Personally, I like the above because it simplifies the macros. But it has a couple of drawbacks. 1. `(virtual_ptr<Animal>, std::ostream&)->void` is not legal C++, `auto (virtual_ptr<Animal>, std::ostream&)->void` is. Isn't this going to cause confusion? 2. Count on MSVC to spoil things. If the return type is explicitly derived from a template, MSVC errors on it. Here is a reduction: #include <string> #include <tuple> template<typename> struct test{}; using foo = test<auto (int)->std::string>; using bar = test<auto (int)->std::tuple<int>>; // MSVC fails on this using baz = test<auto (int)->decltype(std::tuple<int>())>; // workaround Compiler Explorer: https://godbolt.org/z/MrbdYbW9Y It looks like a parser bug, I reported it. To all those who did _not_ suggest this change, if you oppose it, please let me know. J-L

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[Bloom] review starts on 13th of May
by Arnaud Becheler 23 May '25

23 May '25

Dear Boost community, The review of the Boost.Bloom library begins today May 13th, 2025, and will run through May 22nd, 2025. Boost.Bloom is a header-only C++ library written by Joaquín M López Muñoz, providing fast and flexible Bloom filters. These are space-efficient probabilistic data structures used to test set membership with a controllable false positive rate and minimal memory footprint. The library supports a variety of configurations and hash policies and is designed to integrate well with modern C++. You can find the library here: - Repo: https://github.com/joaquintides/bloom - Documentation: https://master.bloom.cpp.al/ Bloom filters are especially useful when: - You need to test if something is not in a large dataset, and can tolerate a small false positive rate. (e.g., avoiding duplicate URL crawls in a web crawler) - You need a memory-efficient structure to represent large sets (e.g., checking for the presence of DNA subsequences across massive genomic datasets) - You want to avoid expensive lookups for items that are definitely not present (e.g., filtering nonexistent records before querying a remote database). As always, we welcome all reviews — from quick impressions to detailed analysis. Your feedback helps ensure that the library meets Boost's high standards in terms of correctness, performance, documentation, and design. If you’re interested in contributing a review, please post to the Boost mailing list during the review period. In your review please state whether you recommend to reject or accept the library into Boost, and whether you suggest any conditions for acceptance. Other questions you might want to answer in your review are: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problems tackled by the library? Note: All links to other parts of Boost in the Boost.Bloom documentation are currently broken, as they were written with the assumption that the library was already integrated into Boost - please do not account for those in your review. Thank you in advance for your time and insights! Best regards, Arnaud Becheler Review Manager, Boost.Bloom

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[bloom] Andrzej's feedback
by Andrzej Krzemienski 22 May '25

22 May '25

Hi Everyone, The following can hardly be called a library review, but I still wanted to give this feedback. The documentation of this library meets what I call the highest standards of Boost. What attracted me to Boost originally was the way the libraries were documented. Studying each new library was learning something new: about programming, about structuring your program, about structuring your thoughts. A lot of libraries, back then, first documented the problem domain, then gave you some theory behind it, then listed possible approaches, and then finally also presented to you the chosen solution. Boost.Bloom represents the same character. I did not know what Bloom Filters were before reading the docs. Now I feel I do. I learned about the problem domain. I was convinced that the problem domain is worth addressing. I know the technical challenges. I know what to expect of the library interface (without having looked at the reference section)! I can already answer one of the review questions. Is the design of the library sound? If the author was able to explain the problem domain and the technical challenges/trade-offs so clearly and succinctly, then I am confident that the library design must be sound. Some interface suggestions: 1. Use the term "bit_capacity" rather than "capacity" for representing capacity in bits. This is not to accidently mislead the users. 2. It is a good move to use the name "may_contain" rather than "contains", but "may_contain" actually also doesn't do justice to the semantics either. The user is asking, "do you contain the value", and the library is replying, "maybe I do, and maybe I don't". Actually, I am unable to suggest anything better. If the function name was `f.definately_misses()` then a true/false answer would be meaningful. and the opposite of "definately_misses" is "either 'contains', or 'misses' incorrectly classified as 'contains'". But I realize that it is longer and contains negatives. So I think your choice of the name is the best given the set of alternatives. 3. When describing the |= operator, use the name "set union", which is the industry standard. The current choice of words "containing both the elements of f and f2" can be interpreted both as a union and as an intersection. 4. I am uneasy about the functionality under &= operator. It implies symmetry with operator |=. But the symmetry is broken for at least two reasons: * If I put some elements to filter f1 and some other elements to filter f2, and then I apply |=, then the effect is the same as if I put all the elements in f1 to begin with. The same property, if I understand correctly, does not apply to operator &=. * The compromising of the FPR value that you are describing. I am not sure if anyone ever needs this intersection behavior. But if it is useful, maybe reflect this lack of symmetry by using a named function rather than an operator? 5. Does the suffix "_for" in the name "fpr_for" bring any value? 6. Not sure if it is a good idea to have two overloads for `reset()` doing slightly different things. For constructors this is unavoidable, but for member functions, you can have `reset` and `reset_for`. 7. I think that you are missing a precondition for operators &= and |=. They work under the assumptions that for both filters f1 and f2 inserting the same element renders the same bit pattern in the hash. But this is not the case when the hashers that I provide to f1 and f2 have the same type but different initial state: filter<T, MyHash> f1(1000, MyHash{1}); filter<T, MyHash> f2(1000, MyHash{2}); The above feedback is based on me having read the documentation. I haven't tried the library, and it is unlikely that I will be able to do this within the review period, so I am not sure if I am qualified to give a recommendation for accepting the library into Boost. Joaquín, thank you for writing and sharing this library! Regards, &rzej;

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Website update
by Robert Beeston 21 May '25

21 May '25

Thanks to everyone who pointed out issues and improvements following the new website launch! We appreciate the feedback, and are working on improvements and remediation. Some of the updates so far include: - Fixed issues with the charconv documentation on both the master and develop branches. - Cleaned up some doc formatting and squashed a bug in the library import logic. - Made sure certain libraries don't get wrapped in a layout they shouldn't be using. - Tweaked the rendering so the docs look more like the original Boost site, closer to what users expect. - Updated the featured video on the homepage to keep things fresh. - Added IPv6 (dualstack) support for AWS S3, improving compatibility and future-proofing. - Swapped out some banner images to keep the look up-to-date. - Fixed links to stl.boost.org We still have plenty to do, and we'll report back when there is more to share. Don't be surprised if you catch the improvements before they are announced. If you do see anything else that needs to be addressed, please feel free to respond here or add a ticket to the repo <https://github.com/boostorg/website-v2/issues/new/choose> Thanks again for your continued patience and support! *Rob Beeston* Creative Director C++ Alliance cppalliance.org

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[Bloom] Some questions
by Ivan Matek 21 May '25

21 May '25

Hi everybody, I was reading the documentation/code, and I have some questions/comments. 1. Why is unit of measurement bit? I understand that conceptually bloom filters(maybe others, did not check) are bit arrays, but for me this seems like very error prone. Would verbose alternative of using boost::bloom::bits(1000) or boost::bloom::bytes(125) be preferred? I did not suggest UDL, as I feel for such rarely used class it may be overkill. 2. boost::hash<short> (and other integral ones) afaik are identity, I presume this is not an issue because you do extra steps if hash_is_avalanching is false, but maybe users should prefer avalanching hash? If so maybe suggest fast avalanching hash available in boost... btw I tried to read the docs but I got(not a big issue, since I read them from original. version): 404 Not Found - Code: NoSuchKey - Message: The specified key does not exist. - Key: develop.bloom.cpp.al/unordered/doc/html/unordered/reference/hash_traits.html - RequestId: JHRNESDX8BYY6T2G - HostId: nz9kkYamNQ4ocu023JneA7PyMHTEyQK9jgMSSBuwReE0OQAslcN0xOZxgopXpvn/63AFQzreXgM= 3. libs/unordered/include/boost/unordered/detail/mulx.hpp contains mulx implementation that seems very similar to one used in bloom, and authors are same. Although this is tiny duplication, would it be best to extract it somewhere to avoid duplication? 4. Is there no benefit in having a power of 2 sized bloom filters? AFAIK it is trick used by hash maps (requires hash is good) to get faster indexing. I see you use clever 128bit multiplication that generates fast mul instruction to avoid division, but I still presume shift and masking would be faster. 5. Why is BOOST_ASSERT(fpr>=0.0&&fpr<=1.0); not BOOST_ASSERT(fpr>0.0&&fpr<=1.0); , i.e. is there benefit of allowing calls with impossible fpr argument? This may sound like nitpicking, but I think it is wrong to allow calls with arguments that give people wrong idea of what bloom filters are capable. I understand that this functionality is under capacity *esimation**,*but I still think it may be confusing. 6. Related to 6. : It is relatively easy to OOM with this if you are "reckless" with fpr value, I would add a suggestion to docs to mention this(if it is not already there, maybe I missed it). 7. It may be just me, but I believe Filter Definition chapter would benefit from visual example, in particular how is BucketSize related to subarray size. 8. Regarding choosing optimal value: In the example we use 10M elements. From what I see they are unused in our computations till the end so I would rewrite: "*Suppose we plan to insert 10M elements and want to keep the FPR at 10−4. The chart gives us five possibilities:*" to something like " Suppose we plan to insert 10M elements and want to keep the FPR at 10−4. Looking up FPR in the chart(this step is not dependent on number of elements) gives us five possibilities:" 9. My IDE complains about redundant inline on member functions. Is this intentionally done since (afaik msvc) some compilers use inline as optimization(inlining) hint or? 10. Should #if 1 in may_contain be there?

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[Bloom] Submit Your Review – Only Two Days Left!
by Arnaud Becheler 20 May '25

20 May '25

Dear Boost community, As a reminder, the review period for the candidate Boost.Bloom library by Joaquín M López Muñoz is set to close in two days, on May 22nd, 2025. If you haven’t had a chance to submit your review yet, there’s still time! All feedback is welcome—whether it’s a quick first impression or a detailed analysis, every comment helps us maintain the quality and standards of Boost libraries. You can find the library here: - Repo: https://github.com/joaquintides/bloom - Documentation: https://master.bloom.cpp.al/ Courtesy from Christian Mazakas, you may want to try out their Boost Nightly demo repository during the Boost.Bloom review period: https://github.com/cmazakas/vcpkg-registry-test If you’re interested in participating but need a bit more time, please let me know—it may be possible to extend the review window slightly to accommodate additional feedback. Thank you to everyone who has already contributed! Best regards, Arnaud Becheler Review Manager, Boost.Bloom

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[openmethod] [policies]
by Jean-Louis Leroy 20 May '25

20 May '25

Hi all, and in particular Joaquín, Christian, Ruben and Steven who contributed remarks on the policy system. I followed some of Ruben's suggestions. There is now a registry that contains collections of classes and methods, and, after initialize(), dispatch data. It also contains a collection of policies. In part this is "just" renaming: what used to be a Policy is now a Registry, and what used to be a Facet is now a Policy. But this is not just cosmetic. The registry mechanism is clearly separated from the policies. Many old facets were CRTP templates, but not always. Now a policy (ex-facet) is - always - a Mp11 quoted meta-function that takes a registry as a single argument. This complicates creating policies a bit, but makes using them much easier, I think. CRTP is gone from the interface (in fact it is hidden). `fork` is gone. The debug and release stock policies looked like this: struct release : basic_policy< release, std_rtti, fast_perfect_hash<release>, vptr_vector<release>, vectored_error_handler<release>> {}; struct debug : release::fork<debug>::with< runtime_checks, basic_error_output<debug>, basic_trace_output<debug>> {}; Now they are: struct release : registry< std_rtti, fast_perfect_hash, vptr_vector, vectored_error_handler, stderr_output> {}; struct debug : registry< std_rtti, fast_perfect_hash, vptr_vector, vectored_error_handler, stderr_output, runtime_checks, trace> {}; An application that wants to use a standard map instead of a fast hash table, and keep all the rest the same, could say: struct my_registry : default_registry::with<vptr_map<>> {}; Or, using an unordered_flat_map: struct my_registry : default_registry::with< vptr_map<boost::mp11::mp_quote<boost::unordered_flat_map>>> {}; I also took Ruben's suggestion of having only one output policy, instead of one for error reporting, and one for tracing. Now, even in release builds, the default handler writes a diagnostic to stderr, before calling abort(). Policies are not aggregated via multiple inheritance anymore. At the moment, I am not convinced with Ruben's approach of making the registry (formerly policy) an object. There would still need to be a static instance of that object, which would contain instances of policy objects. Six of one or half of a dozen of the other. From there Ruben suggested making the dependencies between policies (ex-facets) explicit, as far as I can see this leads to a mess of conditionally enabled constructors. You can see the changes here: https://github.com/jll63/Boost.OpenMethod/pull/22 It's still a draft. The documentation is not yet updated, I'll do a big doc pass when things stabilize again. If you want to post comments directly to the PRs, drop me a line and I will invite you as a collaborator. J-L

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Fwd: [Boost-docs] SGI STL Documentation gone from Boost website ?
by René Ferdinand Rivera Morell 19 May '25

19 May '25

---------- Forwarded message --------- From: Adder via Boost-docs <boost-docs(a)lists.boost.org> Date: Mon, May 19, 2025 at 5:31 PM Subject: [Boost-docs] SGI STL Documentation gone from Boost website ? To: <Boost-docs(a)lists.boost.org> Cc: Adder <adder.thief(a)gmail.com> Dear Authors of Boost and Maintainers of the Boost website, I used to find it useful to find the original STL Documentation on the Boost website, but now https://www.boost.org/sgi/stl/ now gives "404 - Page Not Found". May I ask whether this is intentional or just an accident, please ? Anyway, many thanks for everything you have been doing !! >:D< Adder _______________________________________________ Boost-docs mailing list Boost-docs(a)lists.boost.org https://lists.boost.org/mailman/listinfo.cgi/boost-docs -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supongas Nada -- Robot Dreams - http://robot-dreams.net

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[review] boost.bloom
by Claudio DeSouza 18 May '25

18 May '25

Hello there, I have spent some time playing around with boost.bloom and my review is ACCEPT. The library is very well written, provides intuitive interfaces that are already common in C++ and familiar to users, and the SIMD optimisations are very impressive. Documentation is exemplary, although I would suggest adding a short summary of how this is not a container despite the similarities in interface but how in practice it differs from a set, so the short of attention can better catch the gist of it. I feel the source code could have been better documented for future maintainers, but that’s of no importance overall. I looked into other implementations for bloom filters, and this boost implementation could be described as “very fancy”, however the user experience has no unnecessary clutter and is friendly enough to the non-expert. I particularly must admit I felt out of depth opining in the implementation in general beyond recognising this candidate stands out in its quality by comparison with other implementations. Bloom looks exactly like the sort of thing boost is known to provide model implementation for, and it seems to be a perfect candidate to boost. A sort of “going back to its roots” IMO. Claudio

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[fsc] New website is up at boost.org
by Joaquin M López Muñoz 13 May '25

13 May '25

As all of you have probably already found out by now, boost.org <http://boost.org> is now hosting the long anticipated new website! This has been a lot of work by a lot of people, and we at the FSC are so happy that the project has finally seen the light and would like to say big thanks to everybody involved. The new website is probably the most visible result of the new Fiscal Sponsorship Model approved by the community in September 2024. Please take a moment to review the site and provide your feedback, either here or by filling an issue at https://github.com/boostorg/website-v2/issues <https://github.com/boostorg/website-v2/issues> Looking forward to upcoming developments in the Boost Project. Joaquin M Lopez Munoz Boost Fiscal Sponsorship Committee

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