In that point I share the views of David P Bird who just opened a new thread: "sharks a truth balancing method" focused on a player's view.
I intended for a while to open on my side a new thread more focused on the view of a program exploring all these "exotic patterns".
No question to be in competition. I"ll contribute to David's thread, but I think better to keep separate both topics and I am convinced David will agree and will contribute as well to that thread;
This thread should not integrate the symmetry of given, on which I have nothing to add, except in the post 2 (definitions)
As that thread intend to be a kind of memory in that field, I open several posts to be updated later with the following content
Post 2: definition of the most common patterns for each family
Post 3: why "exotic" patterns are not at all exotic. (in my opinion)
Post 4: extended (generic) definition of the "exotic patterns".
Post 5: Exploring a puzzle after direct effect of a SK loop
Post 6: Exploring a puzzle having an Exocet pattern
Post 7: reserved
Those statistics are extracted from my data base of all "potential hardest" known. here
The selection criteria to enter that data base is the Sudoku Explainer rating (turning now to skfr rating).
after an analysis of the first 30 000 puzzles in that data base, I got the following results
- Code: Select all
20952 puzzles have an Exocet pattern
4954 have a double exocet, the most active tool
1259 have also a "shark" pattern (multi_fish)
4896 have one or more shark pattern
1700 have an SK loop
68 only have a symmetry of given
I am missing a very important reference , the first use of the SK loop
If I am right, "steve k" posted it first in October 2007 on the Eureka forum.
At that time, my solver had produced one of these boring solutions using AIC's nets.
If the use of the SK loop as start did not make the puzzle trivial, it brought such simplifications that I immediately introduced it in my solver. (the infrastructure was ok for that).
The second important reference is the work done by Allan Barker. He first exposed the logic of the Exocet, he first built huge SLGs and it's program is an important tool to check the validity of an assumption and to summarise it with nice graphic presentations
Here some of the key references
Allan Barker site
and some key threads in that forum
based on Allan Findings, the first Exocet work in that thread