Why is a naïve C++ matrix multiplication 100 times slower than BLAS?

Question

I am taking a look at large matrix multiplication and ran the following experiment to form a baseline test:

1. Randomly generate two 4096x4096 matrixes X, Y from

Answer 1

I don't know how reliable the information is but Wikipedia says that BLAS uses Strassen's algorithm for big matrixes. And yours are big indeed. That is around O(n^2.807) which is better than your O(n^3) naïve alogrithm.