The versions below, No.1146.1;2, are published after the end of tournament, 28.10./12.11.2017, but before the award is made, accepted by the judge of PG/Retros 2015-16.
Julia, the n° of this diag is 1146 !
Dmitri’s Py2Web is priceless for such problems.
It makes me aware that I don’t actually see why not 11.Rxg1/17.Kd3.
Because after 11. Rxg1 Sc6, 12. Qd8 results in a recolouring of Sd1.
Nice line-closing and of course unexpected for those (it’s me) who unduly but stubbornly look for the answer only on e,f,g files.
Personally, I think the chance of this being correct is less than 1%, but it takes too much time to find the cook.
This solution was found by an experimental fairy PG solver I’m working on. The program uses heuristics to search the most likely moves first, and this problem seemed like a good test given Joost’s comment. In 25 min it found cooks in both 16.5 and 16.0 moves. Letting it run for 13h, it found the cook shown above in 15.5 moves.
My program looks really promising so I’ll keep working on it and I plan to make it available. Timescale: a few months.
Even if the problem has been broken, I am glad that we finally have such a versed solver in Canada. Congratulations, Francois! A little question: If the last white move is dropped, is the problem still cooked?
Finding this cook was harder for my program than for 1146. It took 15h to find this cook on my computer. Trying in 16.5 moves, it hasn’t found any cook after 43 hours.
A very hidden alternative game, virtually impossible to discover with the human brain. Chapeau!
1146.2 isn’t C+, contrary to what the caption says. At publication time the problem had merely survived 4 days of “demolition mode” on my computer. In an unfortunate game of “Chinese whispers” between me, Paul and Julia, this information turned into “checked for 4 days” and then into the label “C+”.
Today the problem has survived 14 days of demolition mode, but all this means is that Jacobi v0.1 finds no obvious cook so far. The problem is still C-.
In this logic, 1146.2 is still C?.
The letter C comes from the word “computer”, so maybe you could write “C-” for a cook found by a computer, but I don’t see why you’d write “computer minus” for a cook found by a human. You’d need four-state logic.
In general, I test all problems which can be tested by Popeye/WinChloe, and mark them as C+ if sound, or in some cases with additional comment about C+/C- by different versions of the programs.
For the problems with fairy elements not implemented in Popeye/WinChloe I’ve used C-, but maybe it would be more correct to use C?
Have changed 1146.2 to C? for now. But this case was really very much confusing for me, as this version was sent by Paul with the comment “Must say that F. Labelle already checked this last version (for 4 or 5 days) with Jacobi and don’t found an alternative game“; some days later there’s another comment “F. Labelle informs that after 9 days of “demolition mode” his computer is still running. It hasn’t found a cook and it hasn’t found the intended solution either“; and later Paul writes again “This problem is sound“?!
But seriously, to mark those problems I can’t test myself with C+, probably I have to ask authors for the reports from their solving programs.
Maybe someone subscribed to every chess magazine can tell us which convention each magazine is using?
Nothing = not computer tested.
Obviously C+ and C- are definitive (relatively to a given program and version), while C? may be changed to C+ or C- some day.
The big question is whether C- should denote a cooked or a not computer tested problem. François said this is 2-1 in favor of not computer tested, but if we add WinChloe’s opinion, this is 2-2!
Wouldn’t it be absurd using C- to indicate an ORIGINAL which a computer has PROVED to be cooked?
Yes Julia, that’s what I say.
C- or C? could mean “not tested” or perhaps that a computer didn’t find the solution which the humans are able to see.
Of course, as this is a retro problem… An amount of retro problems are 100/100 correct because the reasoning is enough easy to avoid any human mistake, but are nevertheless C? because computers can’t handle such retro problems, even trivial for human brains.
This is a spectacular alternative solution. Thank you, François, for your patience!