[Article] update to Zattera's slot machine

[Mauro]

Coverage gets quite good: ~100%. Nbits_tokens is 488975, and Nbits_tokens/Coverage is 490014, quite good values. Loop-Lay was slightly better, at Nbits = 486946 and Nbits/Coverage = 487859. The best grammar I ever found (unpublished in detail, just posted in a thread) improves a little more:

Does the number of allowed loops affect Nbits in any way? Assuming the same slot assignments achieve 95% coverage for 4 loops and 100% coverage for 5 loops, is it possible for the Nbits score to be worse for the second grammar?

The lower the coverage the lower Nbits will be, because less tokens are encoded. That's why now I don't use the raw Nbits as a metric, rather Nbits/Coverage.  Ie. if you look at one of the tables of my post above (2 repetitions Model C):

Grammar name: PROVA Voynich Ninja Labyrinthinesecurity, max repeats = 2

....

Word types coverage (excluding word types with rare characters): 0,4767848


Total number of bits required (all [encodable] tokens): 350486

Nbits_tokens/Coverage metric: 735103,093436505

This grammar has a low coverage, ~47%, so it encodes only a part of the text and, indeed, it has a very low Nbits (328908). But Nbits/Coverage is 735103, much higher i.e. than the 481947 of my 'best' grammar.

Or, in other words: the original Nbits metric is okay when comparing grammars with a similar coverage (as I did in my article, Nbits/Coverage was just in a footnote), but one needs Nbits/Coverage (or some analogous formula) in the more general case, where the coverage changes. And, in effect, better always use Nbits/Coverage. Sorry for the confusion!