I’m trying, without success, to find a good resource to learn how to do fast exponentiation of a square matrix, one of the requirements for problem COOK50 WW2. Is there anything any of you could reference here? I’m assuming that I really need that promised O(n^3) performance (which I figured out in my frustrated searchs) to have a chance beating the N^9 problem constraint.

EDIT: forget about the implied relation between n^3 and N^9, obviously they don’t relate, and if they did I would be doomed anyway. the n^3 I mentioned was because I saw someone talk about using a formulate to calculate this based on the eigenvalues and eigenvectors of the original matrix, does that makes sense?