[sgtnoodle]

Sure, why wouldn't it be? As far as a cache is concerned, I don't think reverse sequential iteration would be any different than forward sequential. The actual RAM accesses may be less optimal if there's some speculative pre-fetching with assumed forward sequential access, but that's conjecture.

[ehvatum]

With some exceptions, hardware prefetch works in terms of ascending accesses. To learn if a particular CPU will prefetch for descending access, benchmarking is essential. Best to use soft prefetch calls if performance is critical.

[chii]

i would suspect that the cache prefetch/prediction could use the "velocity" of the memory access to predict the next access; so if the access pattern was going backwards, the "velocity" would be negative, but prefetching would still work if they just followed the predicted pattern.