[jpc0]

I understand that entirely, a link list is a non-contiguous heap based data structure.

What I am saying is if you store a reference to an item in a Vec or an index to an item to a Vec it is an implementation detail and looking up the reference or the index generates effectively the same machine code.

Specifically in the case that I'm guessing they are referring to which is the optimisation used in patterns like ECS. The optimisation there is the fact that it is stored contiguously in memory and therefore it is trivial to use SIMD or a GPU to do operations on the data.

In that case whether you are storing a u32 or size_t doesn't exactly matter and on a 32bit arch is literally equivalent. It's going to be dwarfed by loading the data into cache if you are randomly accessing the items or by the actual operations done to the data or both.

As I said, sure use an index but that wasn't the initial discussion. The discussion was doing it to get around the borrow check which is effectively just removing the borrow checker from the equation entirely and you may as well have used a different language.

[IX-103]

The main benefit from contiguous storage is it can be a better match to the cache. Modern CPUs read an entire cache line in a burst. So if you're iterating through a contiguous array of items then chances are the data is already in the cache. Also the processor tends to prefetch cache lines when it recognizes a linear access pattern, so it can be fetching the next element in the array while it's working on the one before it.