The optimal cache usage would be to not use staright nested for loops, but to segment the whole image recursively. So take the whole imahe, then take each quart

The optimal cache usage would be to not use staright nested for loops, but to segment the whole image recursively. So take the whole imahe, then take each quarter, then proceeds each quarter again. At least that is my understanding of how to implement a cache oblivious algorithm. See https://en.wikipedia.org/wiki/Cache-oblivious_algorithm https://en.wikipedia.org/wiki/Cache-oblivious_algorithm Used that approach once when computing a large cross product and it gave a good speed up.