The problem is not with the programs representation , although even that can be a problem. The problem is that your software needs to run on hardware which has

The problem is not with the programs representation , although even that can be a problem. The problem is that your software needs to run on hardware which has real performance and behaviour. Objects are larger than raw data, their this usually means that less data will fit in caches, therefore performance can suffer. Everyone says that this kind of thing doesn't matter, it.all adds up, and it matters to me.