Shortest-proof-game challenge

(5951, Leither123)

@5952

Not that bad! The knight twin is perfect. Similarities in the solutions are often a plus but identities (like the last two black moves) not so much. But there are some 'filler' moves in almost every proof game!

One of several proof games in 7.5.

Yes! I tried to find 6.5 but that looks impossible. Btw, it is standard practice to specify the number of moves in composed SPG's. People with proof game solvers don't care because the solving programs find the shortest one anyway bur for humans it's hard without a number. Especially when it's unknown if the SPG is sound!

Actually, proof game programs require that the move count be specified. Short of a lucky guess when submitting a position, multiple attempts are needed to find the SPG, and further submissions are required to verify it really is the SPG.

This was also my initial solution. Here's one of the alternates:

I've noticed how most people on this forum tend to not include the length of the SPG, although most of the time it is because the position was randomly generated, so nobody has an SPG yet. However, even when I have an intended solution, I usually omit the intended move length in order to make the SPG more difficult to find, which I suppose is a little uncharitable.

Your assumption is correct. The recent posts gradually shifted from random diagrams to designed unique proof games. In the random diagrams the shortest number of moves is yet unknown so "finding an even shorter proof game" is always part of the challenge. Even when they are concluded nobody dare claim that the last version is the shortest possible one. For instance I always found shorter versions for those random diagrams whenever I tried!

Designed proof games are very different. Not only does the composer know the solution, he is also responsible for making sure it is correct. Which includes making sure there are no other solutions beyond the designed thematic alternatives. That becomes more important when also the number of solutions is unknown such that the solver cannot know what he is to find. E.g. I quickly saw there are too many unthematic solutions but couldn't tell if the composer intended shorter solutions and how many. So in creations like this one it is vital to specify the number of moves and the number of solutions unless the complete challenge was C+ tested on all intended solutions.

In the composition community the argument of "difficulty" to hide the number of moves for almost any solving challenge is rejected. Endgame studies are an exception because solvers can objectively identify that they found the correct solution on the basis of their chess knowledge (and by tablebase today). For most challenges they need the feedback of something telling them "mate in 4 is not good enough you gotta do it in 3". So indeed not giving the number of moves (and number of solutions) is harder but it is also considered an unfair challenge. Another well -known example are the helpmates which quite often have 2 to 4 solutions. It is immensely irritating to a solver not to know how many more solutions he must find after the first one! Imagine you believe there are 2 and must conclude there is just one after wasting many hours to find more. And finally, everyone knows that composers are not flawless. Specifying the (theoretically redundant) details of the objective enables the solver to find flaws the composer was unaware of before engaging in an infinite goose chase. So SPG challenges follow the format: SPG in x moves, y solutions.

Btw, chess.com puzzles are all outside the composition standard. Not because it is harder that way, or it is better, or they believe in it - but only because chess.com is 100% geared towards game play where nobody ever tells you it's mate in 3.. They really have no clue what a puzzle is, let alone a composition!

Btw, to illustrate my point, I did waste many hours on your SPG(s) until I read in subsequent posts that the goose I was chasing after had never seen the light of day

Well, worry no more, as I will now present a position with an intended length.

I intend for this to have PGs in 10.0, and I have my own solution ready (though I feel there are more solutions). To be honest, I didn't bother checking thoroughly to see if it's possible to get below ten, so feel free to try getting there

(Interestingly, due to the way I created the positions, the move length is hidden in the FEN! Has anyone noticed this before?)

Yes, I did! A bit late or I would have aborted my attempts to find an SPG in 6.5 earlier! FENs don't count in serious compositions - not the number of moves, not the proximity of the 50-move line, not the side on move, not the castling rights or anything else in the FEN.

ONLY THE DIAGRAM + the text of the challenge (stipulation).

If I understand you well this one has one intended solution in 10.0 moves. Or is it two? Tomorrow I'll look!

Unfortunately, I have now discovered multiple solutions to the position. But the shortest amount of moves is still 10.0, hopefully.

If you ever want a cursory check at your positions, Jacobi has a proof game website where you don’t even have to download an engine.

Thx! Didn't know that. I'll check it out!

Sounds useful! Is this the website?

https://wismuth.com/jacobi/latest/solver.html

For this position, Stelvio finds there are many solution in 10.0, none in 9.5, many in 9.0, none in 8.5, and none in 8.0.

Should be.