Loop-Tiling to Rotate a Matrix

Question

I'm trying to write a function to rotate an image matrix using the loop-tiling technique. However, I'm running into some issues with getting it to work properly.

EDIT: Here's my updated code that works, but only when n is a multiple of the block size. How would I go about handling varying matrix sizes? Right now, I'm just using square blocks, and it works very well for those square blocks. How would I go about changing this to use rectangular blocks based on the size of the array I'm given. Specifically, if I'm given an nxn array, how do I choose the rectangular block dimensions to split it up into?

  //Block size to tune
  int block = 20;
  int i1, j1, k1,  i, j, k;

  for(i1 = 0; i1 < n; i1 += block) {
    for(j1 = 0; j1< n; j1 += block) {
            for(i = i1; i < i1 + block; i++){
                for(j = j1; j < j1 + block; j++){
                    dest[getInd(j, i, n)] = src[getInd(i, n - 1 - j, n)]; 

                }
            }
        }
    }

}

Answer 1

The first two for loops look wrong:

  for(i1 = 0; i1 < n/block; i1 += block) {
    for(j1 = 0; j1< n/block; j1 += block) {

should probably be:

  for(i1 = 0; i1 < n; i1 += block) {
    for(j1 = 0; j1 < n; j1 += block) {

When that's corrected though you'll probably just need to step through the code in your debugger to work out what else needs fixing.