Clojurians Log v2

Just getting started with neanderthal. The native version works well on my mac, but now having difficulty developing on another computer while my mac is repaired. How can I write neanderthal code that prefers a native implementation, but falls back on slower Java implementation when ATLAS is unavailable? It looks like I can choose between native vs GPU based on using the matrix constructors in the native and opencl namespaces, but I don't see similar options for the slower Java option. My current code, which only works with the native implementation, is here: https://github.com/ericlavigne/mlearn/blob/master/src/mlearn/week1.clj#L20