`std::vector` is often said to be the default container, because it provides good baseline performance for common operations. Recently, I experimented with a simple API change that can improve the performance of a common usage pattern by 10+ %.
std::vector::reserve + std::vector::push_back in loop is sub-optimal, because push_back needs to check for re-allocation, but that never comes.
std::vector::resize + std::vector::operator[] in loop is also sub-optimal, because resize default-initializes all elements only to be overwritten soon anyway.
This article’s author suggests push_back_unchecked.
I suggest std::vector::insert with pair of random access iterators with custom dereference operator that does the “transform element” or “generate element” functionality. The standard will have resize_and_overwrite hopefully soon.
std::vector::reserve + std::vector::push_back in loop is sub-optimal, because push_back needs to check for re-allocation, but that never comes.
std::vector::resize + std::vector::operator[] in loop is also sub-optimal, because resize default-initializes all elements only to be overwritten soon anyway.
This article’s author suggests push_back_unchecked.
I suggest std::vector::insert with pair of random access iterators with custom dereference operator that does the “transform element” or “generate element” functionality. The standard will have resize_and_overwrite hopefully soon.
Moar discussion:
https://codingnest.com/the-little-things-the-missing-performance-in-std-vector/
https://twitter.com/horenmar_ctu/status/1695823724673466532
https://twitter.com/horenmar_ctu/status/1695331079165489161
https://www.reddit.com/r/cpp/comments/162tohr/the_little_things_the_missing_performance_in/
https://www.reddit.com/r/cpp/comments/162tohr/the_little_things_the_missing_performance_in/jy21hgd/
https://twitter.com/basit_ayantunde/status/1644895468399337473
https://twitter.com/MarekKnapek/status/1645272474517422081
https://www.reddit.com/r/cpp/comments/cno9ep/improving_stdvector/