measurements/samples) and only one iteration (in Nonius there was 100 Why is RTTI needed for non-polymorphic typeid? If we will try to change the value of any element in vector of thread directly i.e. vector pointer vs vector object - C / C++ How do I initialize a stl vector of objects who themselves have non-trivial constructors? Windows High Performance Timer for measurement. As pointed out in Maciej Hs answer, your first approach results in object slicing. 1. And pointers come with their lot of constraints: they have their own semantics, they make things harder to copy objects, etc. The vector wouldn't have the right values for the objects. thread_local static class is destroyed at invalid address on program exit. Lets make a comparison: The memory is allocated on the heap but vector guarantees that the mem block is continuous. visible on the chart below: Of course, running benchmarks having on battery is probably not the Notice that only the first 8 C++ difference between reference, objects and pointers, Moving objects from one unordered_map to another container, store many of relation 1:1 between various type of objects : decoupling & high performance, Atomic pointers in c++ and passing objects between threads, Using a base class as a safe container for pointers, STL container assignment and const pointers. Containers of pointers let you avoid the slicing problem. If you need to store objects of multiple polymorphic types in the same vector, you must store pointers in order to avoid slicing. Does it need to stay sorted? benchmarking libraries for Bounds-Safe Views for Sequences of Objects Heres the corresponding graph (this time I am using mean value of of A little bit more costly in performance than a raw pointer. That is, the elements the vector manages are the pointers, not the pointed objects. And also heres the code that benchmarks std::sort: When you allocate hundreds of (smart) pointers one after another, they might end up in memory blocks that are next to each other. Some of the code is repeated, so we could even simplify this a bit more. Inside the block, there is a place to store the reference counter, the weak counter and also the deleter object. Learn how your comment data is processed. It all depends on what exactly you're trying to do. Same as #2, but first sort Using a ptr_vector you would do it like this: This would again be used like a normal vector of pointers, but this time the ptr_vector manages the lifetime of your objects. A view from the ranges library is something that you can apply on a range and performs some operation. You may remember that a std::span is sometimes called a view.Don't confuse a std::spanwith a view from the ranges library(C++20) or a std::string_view (C++17). What operations with temporary object can prevent its lifetime prolongation? This is 78% more cache line reads than the first case! * Min (us) Any other important details? Sometimes you want a vector of objects, sometimes you want a vector of pointers to objects, and sometimes you want something else entirely. Ask your rep for details. Note about C++11: reference_wrapper has also been standardized in C++11 and is now usable as std::reference_wrapper without Boost. Vector of Objects vs Vector of Pointers - C++ Stories We get similar results to the data we get with Nonius: Celero doesnt give you an option to directly create a graph (as C++: Defined my own assignment operator for my type, now .sort() wont work on vectors of my type? Click below to consent to the above or make granular choices. There, you will also be able to use std::unique_ptr
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