I think this will be an even more meaningful discussion if you can identify an overhead or a redundant computation in the reduction of k-means to matrix and lin

I think this will be an even more meaningful discussion if you can identify an overhead or a redundant computation in the reduction of k-means to matrix and linear algebraic operations. BTW specific APIs are a different matter, they can and do entail overheads unless compiler optimization and runtime JIT can remove them. If there aren't any redundant operation, matrices give a good abstraction that does not leak much. Libraries take care of the best use of cache. If you have to build castles out of individual grains of sand and burnt clay, it will limit how many of them you can build. That's why building blocks are useful. Where the building blocks don't quite fit, there is always sand, clay and mortar to fill the gaps.