1. fast_perfect_hash achieves performance(load factor) I would assume is impossible, based on perfect hashing talk <https://www.youtube.com/watch?v=yOo6GnbKzp8>. I presume reason why it works so well that compiler places type info data clustered in same region of addresses... Is that correct?
I don't think it is a factor. And counting on clustering would be a rabbit hole all the way to compiler-specific behavior hell. Joaquín and I discussed this in Madrid - we were both speakers at the "using std::cpp" conference. I think it boils down to: - I make many more attempts with the same number of buckets. - My hash function is very simple. - For my purpose, speed matters, not space. Maybe Joaquín wants to jump in, I don't want to put words in his mouth ;-)
2. regarding static_list: would Boost.Intrusive list work here also, and if so was this considered?
Yes. static_list needs to work in a special context: static construction time.I.e., no guaranteed construction order across translation units. Its default constructor does nothing. It relies on zero-initialization. I remember that Boost.Intrusive lists had customization points, but not what I needed. Unless I missed something...
3. basic_error_output does not seem to need the Policy template parameter, is this left for consistency or am I wrong that it is not needed?
It is needed because it has static state: template<class Policy, typename Stream = detail::ostderr> struct basic_error_output : virtual error_output { static Stream error_stream; }; My policy's error_stream is not your policy's error_stream ;-)
4. dynamic_cast_ref docs <https://github.com/jll63/Boost.OpenMethod/blob/ea7dbe86b511797f0281ef07b3ada645fe569328/doc/custom_rtti.adoc> mention that D must match the reference category of B. Would it be possible to static_assert that?
Probably this is a better place, in core.hpp: template<class Policy, class D, class B> auto optimal_cast(B&& obj) -> decltype(auto) { if constexpr (requires_dynamic_cast<B, D>) { return Policy::template dynamic_cast_ref<D>(std::forward<B>(obj)); } else { return static_cast<D>(obj); } } Enforce the contract at the source. Good suggestion though... On Thu, May 1, 2025 at 6:33 PM Ivan Matek via Boost <boost@lists.boost.org> wrote:
Hi everyone, few questions:
1. fast_perfect_hash achieves performance(load factor) I would assume is impossible, based on perfect hashing talk <https://www.youtube.com/watch?v=yOo6GnbKzp8>. I presume reason why it works so well that compiler places type info data clustered in same region of addresses... Is that correct? 2. regarding static_list: would Boost.Intrusive list work here also, and if so was this considered? 3. basic_error_output does not seem to need the Policy template parameter, is this left for consistency or am I wrong that it is not needed? 4. dynamic_cast_ref docs <https://github.com/jll63/Boost.OpenMethod/blob/ea7dbe86b511797f0281ef07b3ada645fe569328/doc/custom_rtti.adoc> mention that D must match the reference category of B. Would it be possible to static_assert that?
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost