You pad the rows manually. Then you start loading bigger chunks of data at a time. Then you start issuing prefetch instructions with compiler intrinsics or inli

You pad the rows manually. Then you start loading bigger chunks of data at a time. Then you start issuing prefetch instructions with compiler intrinsics or inline assembly. Then you ask "why am I dealing with this at all?" and use Intel's math libraries. And finally you use Octave or Matlab. Unless you are a nutter like me, in which case you hand-roll everything in assembly.