Boris Rasin <boris <at> pointx.org> writes:
On 5/5/2015 7:49 PM, Joaquin M Lopez Munoz wrote:
TONGARI J <tongari95 <at> gmail.com> writes:
If the data sequence shows some affinity, I guess an ordered tuple_vector-based sequence can provide some performance benefit in traversal (with some crafted for_each method).
That is, a sequence of [AAABBB] may be traversed faster than [ABABAB] for such a container, and I believe in the later case such that the types are uniformly distributed, vector<variant> will perform better. I wrote something on this some time ago, maybe worth having a look at:
http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections.html http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections-with.html
Interesting read, thanks for the links. Although in this case we are talking about vector<variant> which stores data by value.
Ok, understood. I've written a small performance test of vector<variant<Ts...>> and sorted vector<variant<Ts...>> vs. a collection class het_collection<Ts...> storing values of the same type contiguously and providing a specialized for_each memfun: https://www.dropbox.com/s/qy9qbf0eyf1itsy/het_collection.cpp?dl=0 Timing for for_each on 1k-10M elements (MSVC 12.0): het_collection;vector_variant;sorted_vector_variant; for_each: 1000;0.0225453;0.0822232;0.0840048; 10000;0.0229827;0.0828214;0.0821378; 100000;0.0229448;0.081315;0.0839802; 10000000;0.0250193;0.0906496;0.0879296; So, unsurprisingly, het_collection does much better as for_each on a vector<variant> needs to check type on each iteration. Sorting the vector so that values of the same type lie together does not have any impact on performance. Joaquín M López Muñoz Telefónica