How to find/build implementation of protocol described in core.matrix.impl.defaults?

I’ve run across some interesting work in the default implementation of householder-qrj protocol (function?) found here:

clojure.core.matrix.impl.defaults/householder-qr (defaults.cljc:2501)

See also this interesting discussion of these implementations, from 2013!

Does anyone know how could I find/build or otherwise use an implementation to experiment with this?