Le 01/03/2017 à 09:32, Joaquin M López Muñoz via Boost a écrit :
Hello,
I'd like to ask for formal review of (candidate) Boost.PolyCollection, a library providing fast containers of polymorphic objects:
https://github.com/joaquintides/poly_collection http://blincubator.com/bi_library/polycollection/?gform_post_id=1643 http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html
Typically, polymorphic objects cannot be stored directly in regular containers and need be accessed through an indirection pointer, which introduces performance problems related to CPU caching and branch prediction. Boost.PolyCollection implements a novel data structure that is able to contiguously store polymorphic objects without such indirection, thus providing a value-semantics user interface and better performance. Three polymorphic collections are provided:
* boost::base_collection * boost::function_collection * boost::any_collection
dealing respectively with classic base/derived or OOP polymorphism, function wrapping in the spirit of std::function and so-called duck typing as implemented by Boost.TypeErasure.
The library compiles and runs succesfully in Visual Studio 2015, GCC 5.2.1 and Clang 3.7. Ion Gaztañaga has kindly volunteered to act as the review manager for (candidate) Boost.PolyCollection. Hi,
thanks for proposing this library Joaquîn. I've surely missed why base_collection is named this way. Is it because the parameter is a base class. Could you confirm? On the documentation you compare base_collection<T> and ptr_vector<T> function_collection<T()> and vector<function<T(U)>> any_collection<Concept> and vector< |type_erasure::|any<Concept>> wondering if a single class with specializations wouldn't help collection<polymorphic<T>> collection<function<T(U)>> collection<any<Concept>> In this way we could have collection<Model, Allocator> BTW, I see that you have in the implementation a detail::poly_collection<Model, Allocator> that is the base of the 3 collections. In your blog there were some comments about a collection of variants. Have you considered adding a variant_collection<Ts...> This collection could support ordering and hash. In addition, it could be preregistered. As the collections are closer to multisets (unordered/not-hash), maybe it is worth using this name. Have you think about using the same design for maps/unordered maps of polymorphic objet (where the key is not polymorphic)? There is a C++ proposal for a polymorphic_value (https://github.com/jbcoe/polymorphic_value/blob/master/draft.md). Your base_collection<T> corresponds quite well to this polymorphic_value<T>, isn't it? Maybe polymorphic_collection<T> or collection<polymorphic<T>> The main difference is the memory management, polymorphic_value can be adapted to use an Allocator. What are the function types passed to for_each whee we have a function_collection or a any_collection? Is a reference to the |value_type? |Do we need generic lambdas? Best, Vicente