Many Intel CPUs have caches that have a number of ways that is not a power of two, but it contains a 3 or 5 factor, corresponding to cache sizes like 2.5 MB, 3 MB, 24 MB or 36 MB.

Regardless of the cache associativity, the leading dimension must always correspond to a size that is a multiple of the cache line size (64 bytes for most CPUs) and the matrix must be aligned to the cache line size.

With that condition fulfilled, the total size of a row or of a column (depending on whether the matrix uses C order or Fortran order) may be optimal as a power of two or not, which should be better tested experimentally on the target CPUs or GPUs.