http://forum.enjoysudoku.com/the-hardest-sudokus-new-thread-t6539.html
In the former thread the last post is now one year old, and the thread has been very far from the player view on many points. The main one is the use of “uniqueness”. In this thread, uniqueness is assumed. Next post tells you why.
The player’s view (not easy to define) remains my motivation to work in this field.
Having free time and still some brain potential to work with my computer (now passed 83), I did several things recently that can help to summarize all the recent work done by active members as coloin, , hendrik monard ,marek Stefanik, mith, Paquita ….
I also needed my own updated base to see what was new in my recent results on the vicinity search, so I must anyway make with my tools a full update of what I have seen. It will likely be available in two weeks. Many options are open to share the results.
In the search for puzzles of potential interest, to avoid redundancy, the use of a canonical morph of a puzzle is unavoidable. It will be the case here. To be posted for a blind resolution, such puzzles should be morphed to a kind of “random morph”. I use as canonical the puzzle morphed to the min lexical solution grid.
Complaints posted cyclically by players refer to the mass of puzzles with no special interest. On the other hand, defining what is of interest for a player is not easy and changes with each player.
For the vicinity search, main source of new puzzles, the minimal puzzle remains the best seed, but this is not necessary the morph to keep in a player database. With the TH pattern, many minimal puzzles have the same PM “after…”. Also, in most publications, the players start with a PM “after ….”
IMO, it makes sense to store hard puzzles “after…”. This excludes, in fact, al puzzles below the “after” and will reduce significantly the size of the file when the TH is there.
The cutoff can be long discussed, but I would be, for hard puzzles, in favor of a cutoff leading to puzzles having no assignment possible using a relatively high rule as “all bi-values”. Such puzzles would show a {sudoku explainer Ed rating} over 2.3 and possibly up to 8.0
In my quick solver, knowing that this filter must be applied to millions of puzzles, the limit is more what I can do in some milliseconds at most. In my current quick filter, the UR/UL cleaning is still missing.
The issue of puzzles having an identified easy solution through exotic patterns is different.
In my first data base, I had flags telling which “Exotic pattern(s)” had been seen (if any).
Such flags give the opportunity to newcomers to select such puzzles to work on a specific pattern. This is IMO better than to try to reduce the list killing puzzles “easy to solve for a skilled player having the clue”
This requires somebody setting the flags using a solver. I did it in the past, but my old solver is not at all up to date to do it today, and I am too old to just think of taking over the burden. BTW, each player can have its own file based on published puzzles of the database.
I have also a small problem with the flow of puzzles posted in the last 2 years. Just gathering, canonizing, filtering redundancy is a huge task. Keeping track of the first appearance is just not possible. Also, as long as puzzles are not posted in the canonical morph, the updating of the database with the “owner” of the puzzle is usually not feasible. Moreover, if only puzzles shown “after..” are stored, the source will usually be multiple (this is the target).