On 05/11/2015 05:41 AM, Jakub Arnold wrote:
Hi, I'm curious as to why libstdc++ is using a RB-tree to implement std::set (details here https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/std/set and here https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/include/bits/stl_tree.h), when there are faster alternatives?
Because the original HP STL that most implementations (including libstdc++) are derived from was written that way. Changing the underlying data structure would likely break binary compatibility and so the benefits of such a change would have to significantly outweigh its costs. Martin
I'm mainly curious, because from all the people I've asked there hasn't been a single answer in favor of RB-trees, other than "they're already popular" or "easy to implement". If you'd like more details on that, here's a link to my question on stackexchange http://cs.stackexchange.com/questions/41969/why-are-red-black-trees-so-popular, where nobody has yet answered as well. TL;DR: Using a variant of B-tree (or (a,b)-tree) should be faster, and everyone seems to suggest so, which makes me wonder what is the reason for picking RB-trees? This is not a question about their theoretical speed, but about real world behavior on real hardware with respect to CPU caches, etc. -- Jakub
