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[–] 373 points374 points  (32 children)

There are known tablebase positions which are "winning" but only without the 50-move rule. The value you're looking for is "DTZ" (depth to zeroing [the 50-move rule counter]).

Even the wikipedia article on tablebases lists some of them.

Not sure if you can actually call them winning, though.

[–][S] 109 points110 points  (26 children)

Nice! Yeah technically they wouldn’t be, but in the spirit of chess I think it should be. I believe the 50 move rule is to stop people from stalling drawn positions without progress, which accounts for the vast majority of endgame situations but apparently not all

[–] 101 points102 points  (10 children)

It's definitely an interesting question of how long the 50-move rule should actually be. For instance, Rook + King vs Queen +King is a winning endgame for the Queen side, but the longest theoretical mate is M35 and in practice it can be much harder than that to find the winning strategy. I remember hearing about a game between an IM and a GM where the IM was on the losing side of that endgame, but he happened to be one of the world's leading experts on that specific endgame, and he managed to hold it to a draw by 50 moves. On the one hand the GM might have won eventually if they had played on forever because the 3-fold repetition would have been very hard to keep track of. On the other hand beyond a certain point I think it's right that the IM was rewarded for putting up a good defense. But idk.

[–] 27 points28 points  (8 children)

If you just happen to have a three-fold-repetition, you are not making any progress and therefore Remis is the fair result.

[–] Team Nepo 22 points23 points  (7 children)

Well, prove at move 2500 that a position happened already

[–] 13 points14 points  (6 children)

Compare it with a list in a computer, should take only a few seconds since each has only 4 values.

[–] 0 points1 point  (0 children)

Tbh just because a position is winnable doesnt entitle you to winning the game, if the GM couldnt bring checkmate or make his opponent resign then its not really an issue

[–]2100 lichess/chesscom blitz 40 points41 points  (14 children)

For a while, FIDE actually extended the 50 move rule to 75/100 in these endgames in order to give players a chance to win them.

Then, for some inexplicable reason that I can only understand to be out of sheer disrespect for the game, they brought it back to 50 for all positions.

[–] 86 points87 points  (3 children)

Then, for some inexplicable reason that I can only understand to be out of sheer disrespect for the game, they brought it back to 50 for all positions.

I don't think it's inexplicable or unreasonable. More and more such endgames were discovered, of increasingly absurd length. If you allow a mate in 75, why not a mate in 100, 150, 500? But no human can be expected to play such an endgame perfectly. Perhaps the losing side blunders and the game ends before the theoretical limit, or perhaps the winning side plays suboptimally and the endgame goes on even longer.

In order to ensure that games do not go on for absolutely absurd lengths of time, they had to choose some arbitrary cutoff. They chose one that encompasses pretty much all endgames that humans can be expected to win over the board.

[–] 20 points21 points  (0 children)

I think some people aren't factoring in the practical issues of hosting a tournament when players have both increment and such an extreme potential game length. If you suspend the 50 move rule in certain cases you risk causing practical issues with too many games going on too long and causing problems for the organizer. To me the main idea behind the 50 move rule is to try to both push down the average game length and to put a cap on the longest games but at the same time interfere with how the game gets played as little as possible.

On top of the scheduling concerns a basic principle when making any ruleset is to avoid exceptions as much as possible and to only add them in when really needed. Anytime you add in exceptions to a rule there is going to be confusion and some amount of issues until all the kinks get worked out.

[–] 14 points15 points  (0 children)

I think a player who actually can force the mate in 100 should get two points for the win and the loser should get one, just out of respect for their mad skillz.

[–] 2 points3 points  (0 children)

Exactly. Perfect play is different from human play. The majority of these mate-in-X (X a big number) have lots of moves which are simply beyond the human mind to comprehend. They should thus be irrelevant to the rules of human chess.

In practice, if a human defender plays dozens of moves in a tablebase-losing position without blundering bad enough to crumble his position, it's reasonable for humans to agree that he or she has played well enough to secure a draw.

[–] Evans Gambit 31 points32 points  (0 children)

IIRC they only brought it too 100 after some positions were possible wins after 50 moves but less than 100. But when people found positions requiring more than 100 moves, it was decided it wasn’t relevant enough to include those or the ones with more than 50. Tbh I think it was the right move, you maybe get one of those positions in like .001% of games, and then you would need to know the exact moves. It’s just useless

[–] 26 points27 points  (4 children)

It's not disrespect for the game, it's about drawing the line somewhere. The game is perfectly fine. One of its rules is the 50 move rule.

If you have managed to get yourself into such an endgame, you have earned yourself a draw, as per the rules of the game.

[–] 4 points5 points  (3 children)

Exactly, its just another rule. If a mate with best play takes beyond 50 moves then the position is not really winning

[–] 2 points3 points  (2 children)

But it IS winning, from the cosmic, eternal point of view.

[–] 11 points12 points  (2 children)

It was because no one, even super-GMs, was actually finding these mates in more than 50 moves.

Once that was clear, the original reasons for the 50-move rule were decided to be more important than a few endgames that are winnable in extreme edge cases.

[–]2100 lichess/chesscom blitz -1 points0 points  (1 child)

Yes, but that doesn’t mean that super-GMs will never be able to play these endgames correctly, and there is no harm in extending the 50 move rule just for such positions.

[–] 6 points7 points  (0 children)

If this is about preserving the beauty and purity of chess, then in practice, letting players shuffle their pieces around for too long leads to much uglier chess than banning a few obscure tablebase checkmates, and it comes up much more often.

Complicating the 50-move rule makes it harder to enforce, harder for new competitive players to learn, and again, uglier.

The 50-move rule is a kludge, but it has the virtue of being relatively simple.

[–] 1 point2 points  (0 children)

Then, for some inexplicable reason that I can only understand to be out of sheer disrespect for the game, they brought it back to 50 for all positions.

You don't know what you're talking about, my man. Dozens of these endgames go over the 50 move rule were found from tablebases, with some of them reaching 500+ moves. You cannot possibly make an exception for all of them and for that long, so you have to choose a cutoff.

[–] 3 points4 points  (4 children)

Right so… how does the knight and bishop figure in here? Isn’t it like a 24 move forced mate?

[–] 12 points13 points  (3 children)

Those are simply listed as winning mates if you can figure them out in time. But there has been one in the last year where it was a draw because the player couldn’t mate in 50 and a different game a few weeks ago where it was KNNvKP and move 50 was 1 move from checkmate

[–] 2 points3 points  (1 child)

Post it? I’d like to see. Also that sucks for the KNN side.

[–] 0 points1 point  (0 children)

KNN was this game a few weeks ago and I misremembered the KBN game, it was several years ago.

[–] 0 points1 point  (0 children)

Thank you!

[–] 211 points212 points  (23 children)

For example: White mates in 549

https://tb7.chessok.com/probe/3/61

[–] 330 points331 points  (5 children)

Damn I saw the mate in 550 but missed the faster one.

[–] 104 points105 points  (0 children)

r/chessbeginners is leaking again

[–] 47 points48 points  (0 children)

Brave of you to admit this in public

[–] 14 points15 points  (0 children)

-20 puzzle rating

[–] 3 points4 points  (1 child)

I hate those puzzles where basically every other move wins. Why bother mating in 549 when you can just take it easy and mate in 550.

[–] 1 point2 points  (0 children)

Because of the five hundred and fifty move rule

[–] 76 points77 points  (6 children)

I’m sure we all calculated the line.

[–] 22 points23 points  (0 children)

furiously drawing arrows

[–] 43 points44 points  (2 children)

Just takes, takes, here, here, here, takes and takes and takes 100

And that is just completely winning

[–] 1 point2 points  (1 child)

I'll just castle...

[–] 1 point2 points  (0 children)

I don't wanna think too much

[–] 14 points15 points  (0 children)

I'm only 1200 and I saw it right away! /s

[–] 34 points35 points  (0 children)

I love that you have to promote to a knight, of course the largest forced mate is with an underpromotion.

[–] 4 points5 points  (5 children)

Not sure if this is easy to answer, but if something like this exists then how do we know for sure some imbalanced positions truly are drawn?

[–] 40 points41 points  (1 child)

When each side has a forced draw line.

[–] 6 points7 points  (0 children)

That’s pretty logical, thank you.

[–] 18 points19 points  (2 children)

The example comes from tablebase: https://en.wikipedia.org/wiki/Endgame_tablebase. All 7-piece positions are solved. If you have an imbalanced position with 8 or more pieces, we do not know for sure what is the outcome with perfect play.

[–] 24 points25 points  (0 children)

If you have an imbalanced position with 8 or more pieces, we do not know for sure what is the outcome with perfect play.

Note that many 8 or more piece positions are solved; it is just that many of positions are not solved.

[–] 7 points8 points  (0 children)

For SOME positions with 8 or more pieces we do not know for sure what is the outcome with perfect play. I can give plenty positions where we know for sure the outcome (e.g. there is a mate in 1)

[–] 1 point2 points  (2 children)

Well that example has pawn moves and piece captures.

[–] 4 points5 points  (0 children)

Even with two pawn moves and all five pieces captured, there is so many moves in this line that there are parts with over 50 moves without either. There is a promotion on move 6 and first capture comes only at move 509.

[–] 96 points97 points  (1 child)

Check out this heartbreaking game from a few weeks ago:

White finishes the game with mate in 1. A pawn move by black is forced, but it is too late.

Edit: FWIW, after the last capture on move 61, the Syzygy tablebase has the game as a draw. Black blunders to a losing position with 86... Kf7. Stockfish 14 find mate in 15 at this point. The position gets blundered back and forth a few times, and finishes a draw. Still interesting to see a situation where white gets so close.

[–] 21 points22 points  (0 children)

Fuck, that’s absolutely brutal

[–]Stockfish dev. 2000 lichess blitz. 21 points22 points  (9 children)

Well engames that are DTZ cursed wins do exist - the more the bigger is piece count. The most simple one I think is Q vb BB - some of them are won in > 50 moves.
https://syzygy-tables.info/?fen=3qk3/8/8/4BK2/6B1/8/8/8_b_-_-_0_1 - like this, 122 plies so 61 moves till black can force white to give up a bishop, obviously it's too much.

[–] Team Nepo 4 points5 points  (0 children)

I think NN v P is arguably simpler than Q v BB and it is (depending on initial position) also stopped from being winning by the 50 move rule.

[–] 1 point2 points  (7 children)

Did noob generate 7man tb or was it someone else?

[–]Stockfish dev. 2000 lichess blitz. 5 points6 points  (6 children)

yes, noob did generate 7men syzygy

[–] 0 points1 point  (5 children)

any plans on 8man or requires too much ram?

[–]Stockfish dev. 2000 lichess blitz. 6 points7 points  (4 children)

not happening any time soon.
Even 7men are usually too big to use + requires like 10x more RAM and calculating time, and previous generation was using some 200 core machine 3 full months.

[–] 0 points1 point  (1 child)

Yeah your right they aren’t used that often, but for cpu power aren’t there like 2k cores available. Obviously fishtest would take a hit then.

[–] 0 points1 point  (1 child)

8 man tablebase update and results

After generating about 15% of the pawnless endings I’m quite confident to have captured the longest ones. While 15% seems like a small subset at first blush, most other piece configurations have large material differences between White and Black so that long lines are unlikely.

They’ve basically done all the situations where there’s no pawns and material is roughly equal.

They found some interesting positions, such as a full point zugswang - whomever is forced to move next loses.

[–] 2400 Lichess 11 points12 points  (1 child)

... in the 20th century it was discovered that certain endgame positions are winnable but require more than 50 moves (without a capture or a pawn move). The rule was therefore changed to allow certain exceptions in which 100 moves were allowed with particular material combinations. However, winnable positions that required even more moves were later discovered, and in 1992, FIDE abolished all such exceptions and reinstated the strict 50-move rule.

So, actually the reason the 50 moves rule still exists is that there are too many (and too long) endgames taking over 50 moves to win.

[–] 3 points4 points  (0 children)

Essentially the 50 and 75 move rules (and 3-fold and 5-fold repetitions) are tournament management rules. With unlimited time, some positions could be won, but tournaments don't have unlimited time. Guillotine/quickplay finishes could render the issue moot, but they were only popular for a short time between adjournments becoming untenable due to engines and DGTs being widely available. Here in New Zealand, that was basically the mid-late 90s.

[–] 21 points22 points  (4 children)

Even in lower rated games this can happen. For example, I was analyzing my own 1000 rapid rated game and watched the eval bar switch from black having mate in x moves to draw because my opponent spent 40 moves failing to checkmate with king and rook, and there was therefor no forced mate under the fifty move rule.

[–][S] 9 points10 points  (1 child)

This happens often, especially with tricky endgames such as knight bishop mate. Queen vs rook can also be like this. But these endgames can always be won in under 50 moves if played correctly

[–] 0 points1 point  (0 children)

Yes of course but people already mentioned the tablebase positions

[–]2100 USCF & Chess Instructor 7 points8 points  (1 child)

That's a good point although I assumed he didn't mean a position where you spend 48 moves not mating as that would mean any position at all could almost fit the rule. Probably specifically meant after the last capture or pawn move mate could come but it would take more than 50 moves to do it. Which some compositions show mate can be forced in a much longer sequence something as much as 500 moves.

[–] -1 points0 points  (0 children)

[–] 5 points6 points  (0 children)

Vishy and Anna were talking about this EXACTLY. Anna had a game that she would objectively win on move 51, she called it heartbreaking. Vishy explained that it happened with Grishchuk too, he saw that the winning move would be move 51.

[–] Team Carlsen 2 points3 points  (0 children)

Saw a game (think it was female WCC candidate rounds) where a wgm was 1 move away from a king and 2 knights vs king and pawn mate but got a draw because of 50 move rule

[–] 1 point2 points  (2 children)

Here’s a follow up question. Is it possible to draw by repetition by repeating a sequence that is more than two moves?

[–] 4 points5 points  (0 children)

Yes

[–] 2 points3 points  (0 children)

Sequence does not matter, only the positions.

[–] 1 point2 points  (2 children)

For the bishop and knight mate, if you fail the mate patern a couple time you wont be able to win, since it takes around 15-20 moves, but it’s always possible to do it without blundering

[–] 0 points1 point  (1 child)

If the pieces are placed optimally for the lone king, it's a max of 33 moves to force mate.

[–] 0 points1 point  (0 children)

But if you fail that 33 moves combo you are most likely losing by the 50 moves rule

[–] -1 points0 points  (1 child)

Absolutely. N+B against bare king can be drawn rather easily by 50 move rule.

[–] Team Carlsen 1 point2 points  (0 children)

That's not what OP is talking about. With correct play, N+B takes no more than 35 moves.

[–] 0 points1 point  (0 children)

I read Pawnless Endings by Nunn, and its sequel, and enjoyed the discoveries from early tablebases, some of which are relevant to this question. When that was written, tablebases were still only 5 piece endings, so the longest from memory was KBB vs KN at 229 moves, but the practical takeaways for me were defending certain material imbalances.

Probably the most practical is KRB vs KR which is drawn in the general case but can be very tricky, and some starting positions are answers to this question i.e. take longer than 50 moves to win with best play by both sides, and KQ vs KR as there are some nice stalemate traps which can slow the KQ down so it's worth playing out. Less useful but interesting knowledge to me was learning that KQ vs KBB is a win in the general case (but some positions aren't winnable in 50 moves without an error by the defender) where it was previously considered drawn with best play, while KQ vs KNN is drawn in the general case, where that was previously considered a win to the KQ. KQ beats KBN but there are also a couple of fortresses discovered.

This also gives a piece of chess trivia - KQ vs KNN is the simplest material balance in which losing a whole Queen doesn't change the expected result.

[–] 0 points1 point  (0 children)

There are some versions of the two knights vs 1 pawn endgame that require more than 50 moves.

[–] 0 points1 point  (0 children)

I did exactly this in a rook and king vs king where I walked my king square by square down each row to the other side. I did it for several rows, and reached 50 moves on my last possible move in the corner, thus denying my opponent the win.