[jcranmer]

One of the ideas behind UNUM is that we're using extra bits to guard against the possibility that we see catastrophic cancellation (the mass loss of significant figures between two nearly-equal values), and using intervals would allow us to only use those extra bits when necessary (as it's a variable-width format). The argument is that unums instead of floats would allow for better packing of memory, and by counting the energy cost per value of memory, it's an overall win.

That argument is rather mendacious, though. Yes, it does cost energy to maintain large register files, caches, and DIMMs, but hardware already aggressively turns that stuff off when not in use. Thus the lowest-power solution is generally the one that maximizes the use of everything. Furthermore, the cache and RAM is generally a fixed cost anyways: you're not going to say "oh, I only need 12GB of RAM instead of 16GB because I can store on average 3 bytes/value instead of 4". Thus the only component you can really claim counts as part of the enum power usage is the register file, and this paper appears to be going with a fixed-width format for doing the hardware computations anyways, so the win there isn't going to happen.