Make use of scratch buffers

[Andersama]

I'd just like to point out, there's a lot of allocations being made in the initialization process which don't need to happen. A lot of std::vector<...> variables could be std::array<...>, and most locations where anything which requires dynamic length could use some form of scratch buffer.

If this tutorial is meant to use the standard library, there's room for improvement by using std::pmr::vector<...> types instead with a monotonic buffer.

[YashwanthCB]

The size of std::array should be passed as a constant during initialization which makes it impossible to be used for almost all use-cases in the tutorial. Also all these logics are arranged in a neat scalable fashion that enables us to add more features without breaking anything. So, i believe they made the right choice in using std::vector. Additionally it is convenient to get size and manage lifetime as well.

I don't know what scratch buffer is. Can you please elaborate?

[slendidev]

While std::array may be faster because it has automatic storage duration of the underlying data compared to std::vector's dynamic storage duration, I do agree that std::array can be quite cumbersome to use, having to specify the size explicitly. I also don't believe that those lead to much of a performance penalty, especially with mature allocators. The suggestion of using std::pmr though is interesting and maybe should be looked into, alongside using a scratch/arena.

I don't know what scratch buffer is. Can you please elaborate?

Basically this: https://en.cppreference.com/w/cpp/memory/monotonic_buffer_resource.html

[YashwanthCB]

Op is asking us to use std::array's memory region for scratch buffer and allocate vectors inside it. seems interesting but feels like an overkill. But i would explore its use-cases.