How frequent are the J-Exocets in the grey zone?For the 5,926,343 puzzles in the controlled-bias collection produced by the controlled-bias generator (*), I had computed long ago:
- the SER for the first 3,037,717
- the W rating for the whole collection (at that time, instead of "W rating", I said "pure NRCZT rating" but it's the same thing).
(*) For details about this, see the "real distribution of minimal puzzles" thread.
Considering only the first 3,037,717:
5615 have SER >= 9.0
2353 have W >= 8
664 have W >= 9
I have looked for JExocets in the 664 W>=9 cases, which corresponds to a stricter definition of the lower bound of the grey zone than SER >= 9.0
I activated JEs and the rules of SSTS - i.e. Whips[1] and (Naked, Hidden and Super-Hidden) Subset rules - and nothing else.
In order to avoid degenerated cases, JE's of any size were assigned lower priority than all the rules in SSTS.
By JE, I mean standard Jk-Exocets, with k = 2, 3, 4 or 5 (as defined in this post
http://forum.enjoysudoku.com/pattern-based-classification-of-hard-puzzles-t30493-85.html). Franken or
Blue's extensions were not taken into account (for the only reason that they are not programmed in SudoRules), but I don't think they could lead to very different stats.
No JExocet was found in any of these puzzles; so, the calculations for a rough estimate of the unbiased frequency in the grey zone shouldn't require a doctorate in statistics and I won't invest more personal time on this topic.
[Added: How frequent are sk-loops?: none found in this sample]