>it's from 2016 so the title should be updated

I will try to update the title. There are no changes since then that diminish this document's value - the einsum notation is still the same. The biggest change since then is that the numpy.einsum implementation has been tremendously optimized and has become the benchmark in capabilities that other libraries follow.

Edit: Opt_Einsum is amazing and was a big part of the optimization efforts - it has been merged fully into numpy since v1.12. See https://github.com/dgasmith/opt_einsum#news-opt_einsum-will-...