I submitted an issue that gives a further >4x speedup with just simple straightforward code (no simd, fastmath or threads). It's important to make everything a

I submitted an issue that gives a further >4x speedup with just simple straightforward code (no simd, fastmath or threads). It's important to make everything a view, and to remember the dots in the right places, otherwise this is quite straightforward. I believe you can get significant _further_ speedups with better simd vectorization and threading. I made this as simple as possible, to be similar to the python/cython code.