Which is most cache friendly?

Question

I am trying to get a good grip on data oriented design and how to program best with the cache in mind. There\'s basically two scenarios that I cannot quite decide which is bette

Answer 1

I understand that this is partly opinion-based, and also that it could be a case of premature optimization, but your first option definitely has the best aesthetics. It's one vector versus six - no contest in my eyes.

For cache performance, it ought to be better. That is because the alternative requires access to two different vectors, which splits memory access every single time you render a mesh.

With the structure approach, the mesh is essentially a self-contained object and correctly implies no relation to other meshes. When drawing, you only access that mesh, and when rendering all meshes, you do one at a time in a cache-friendly manner. Yes, you will eat cache more quickly because your vector elements are larger, but you won't be contesting it.

You may also find other benefits later on from using this representation. ie if you want to store additional data about a mesh. Adding extra data in more vectors will quickly clutter your code and increase the risk of making silly errors, whereas it's trivial to make changes to the structure.