Cursed win at TCEC

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Evert
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Re: fortress_draw_rule

Post by Evert » Sat Nov 19, 2016 9:58 am

Lyudmil Tsvetkov wrote: Rules should be changed, when they are unjust, which is precisely the current case.
The rule in unjust in your opinion, which is not fact.
The game was already a white win: SF had been showing 105cps from the early mg, Houdini some 80cps. That is a win, however you would like to look at it.
So evaluating a position at +0.80 constitutes a win? This is new to me.
I for one don't think this is a rule that should be adopted.
Why penalise SF because some tablebase rule artificially prunes the mating sequence, rendering it a draw instead?
Tablebases have nothing to do with it other than telling you with absolute certainty what the outcome of perfect play under a set of rules would be.
In this case the outcome is different if the 50-move rule is observed and if it is not.

So is the 50 move rule observed? Yes, it is. Is the position a draw under the 50 move rule assuming perfect play by both sides? Yes, it is.

Do you like the 50 move rule? Apparently not. That's an entirely different discussion though.
The claim that H went for the tb position because it saw it is 0.0, and otherwise black had better options, is simply wrong, as, most probably white had a win throughout.
Proof it.
You don't get away with saying you can "probably" proof it.

Note that Stockfish played by the same rules and had access to the same table bases as Houdini. So if Stockfish had a way to salvage the win, it missed it and squandered the point. That's all in the game.
Concerning your ridiculous claim that KP vs K with stalemate position also favours white, but is still a draw, how on earth you compare this absurd position with the tbs mate? In KP vs k and stalemate, the position is simply draw, as there is no mate,
Yeah, there is. Stalemate, which the rules say is a draw. The rules of chess are not set in stone and can and historically have changed. Stalemate used to be a win. Hell, baring the enemy king used to win the game.
Yet under the current rules, the position is a draw. The 50-move rule is really no different.
while in the referenced TCEC position, this is a win, there is mate.
Yeah, but unfortunately not within 50 moves. So the win is cursed.

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Evert
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Re: fortress_draw_rule

Post by Evert » Sat Nov 19, 2016 10:12 am

Lyudmil Tsvetkov wrote: 1) the rule is unjust, it penalises the side having a win, you artificially transform a win into a draw.
It certainly makes the game more draw-ish, and you're perfectly allowed to make a chess variant that doesn't employ the 50 move rule. It'll be a different game, with different strategy in the late end game.

Let me ask you this though: why is it more unjust to rob the side with a win of their win, than to rob the side that can escape with a draw of their escape?
2) what is the purpose of wdl, when, according to current rules, W=D?
Where does it say that?
3) tablebase mates in more than 50 moves are relatively frequent, there are at least 500 of those discovered as of now, certainly more will be added later; why take a blindfold stance, claiming those are all draws?
Because adding exceptions for all of them is unmanageable?
They used to have exceptions when tablebases first showed long wins in certain end games, and quickly realised that allowing these is a Pandora's box that leads to so many exceptions that the whole thing becomes unwieldy.
4) my artistic sense gets bitterly offended, when all side's efforts and an objectively won position are declared a draw; I guess everyone else's artistic sense gets offended too?
Objectively won under a set of rules that you prefer, but which are not the rules under which the game is played.
It's important to understand that "Chess" does not refer to one game. It refers to a family of (closely) related games with rules that are similar but may differ in subtle (or not-so-subtle) ways. Chess played under FIDE rules is a different game from Chess played under Correspondence rules. The rules for problems are different again.
5) rule is simple to implement and without detriment to the overall game development; you split the rule into 2 portions, one concerning the general 50-moves rule for the standard game situation, not to make the game too long, and a second one providing for the specific case of pawnless endgames, where the 50-moves rule will be adjusted to 100-move rule or higher, to accomodate the won endgames. Very simple.
Makruk has something like that, but the other way around. If you find yourself in a pawnless endgame and still have two rooks remaining, you have at best 4 moves to mate the enemy king (fewer if you have more material remaining). Hope you considered that before capturing that last pawn!
This deeply affects strategy in the end game.

Now, you're perfectly agreed to make a chess variant that uses your rule as an alternative to the 50-move rule. Knock yourself out. If it proofs to be popular, it may replace FIDE Chess eventually.
6) Rules change with progress. Until we knew there are tbs wins longer than 50 moves, the 50-move rule was adequate, now, when we know there are such longer wins, the 50-move rule becomes outdated and should be changed.
Why?
Because you prefer that? Not all of us share your personal preference.

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hgm
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Re: fortress_draw_rule

Post by hgm » Sat Nov 19, 2016 10:19 am

I always thought it very unjust when I am two Pawns ahead in an end-game with unlike Bishops, and cannot make any progress towards a win because the opponent is blocking my Pawns on the other color than my Bishop. It is really unfair that I am not allowed to put my Bishop on the other color. An advantage of two Pawns obviously is enough to make it a totally won position, and this artificial rule that constrains my Bishop to one color spoils it. If we organize an engine tourney we should certainly adjudicate such positions as a win for the side with more Pawns, if it could be won by stepping the Bishop to teh other color! :lol: :lol: :lol:

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Re: fortress_draw_rule

Post by Joerg Oster » Sat Nov 19, 2016 10:28 am

hgm wrote:I always thought it very unjust when I am two Pawns ahead in an end-game with unlike Bishops, and cannot make any progress towards a win because the opponent is blocking my Pawns on the other color than my Bishop. It is really unfair that I am not allowed to put my Bishop on the other color. An advantage of two Pawns obviously is enough to make it a totally won position, and this artificial rule that constrains my Bishop to one color spoils it. If we organize an engine tourney we should certainly adjudicate such positions as a win for the side with more Pawns, if it could be won by stepping the Bishop to teh other color! :lol: :lol: :lol:
ROFL! :lol:
Jörg Oster

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Evert
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Re: fortress_draw_rule

Post by Evert » Sat Nov 19, 2016 11:13 am

hgm wrote:I always thought it very unjust when I am two Pawns ahead in an end-game with unlike Bishops, and cannot make any progress towards a win because the opponent is blocking my Pawns on the other color than my Bishop. It is really unfair that I am not allowed to put my Bishop on the other color. An advantage of two Pawns obviously is enough to make it a totally won position, and this artificial rule that constrains my Bishop to one color spoils it. If we organize an engine tourney we should certainly adjudicate such positions as a win for the side with more Pawns, if it could be won by stepping the Bishop to teh other color! :lol: :lol: :lol:
Why go through all that effort? Just adjudicate the position as a win when the score reaches +2.
I'm not sure that both engines need to score it as +2 either. I think only the winning engine has to show the winning score. After all, it's possible that the other engine just lacks this knowledge.

Now excuse me while I go and add a "score multiplier" to all of my engines.

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Re: fortress_draw_rule

Post by hgm » Sat Nov 19, 2016 11:19 am

Actually I seriously considered doing the opposite: use a 10-fold score divider for negative scored. When I learned that CCRL habitually adjudicates dead draws as losses just because your engine prints too negative a score, I figured this could bring in some cheap Elo.

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Re: fortress_draw_rule

Post by syzygy » Sat Nov 19, 2016 12:05 pm

Lyudmil Tsvetkov wrote:5) rule is simple to implement and without detriment to the overall game development; you split the rule into 2 portions, one concerning the general 50-moves rule for the standard game situation, not to make the game too long, and a second one providing for the specific case of pawnless endgames, where the 50-moves rule will be adjusted to 100-move rule or higher, to accomodate the won endgames. Very simple.
So you get dozens of rules for specific endgames that change as more TBs are being generated and as more specific endgame positions are being solved by Freezer- and Finalgen-like programs. Nobody will be able to keep track of that, but never mind. Simple yes, but only if you prefer to be very naive.
6) Rules change with progress. Until we knew there are tbs wins longer than 50 moves, the 50-move rule was adequate, now, when we know there are such longer wins, the 50-move rule becomes outdated and should be changed.
So FIDE has done that already and came to regret it for the obvious reasons already stated. They therefore reverted to the exceptionless 50-move rule, which just works and is fair and predictable.

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Re: fortress_draw_rule

Post by syzygy » Sat Nov 19, 2016 12:55 pm

Evert wrote:
Lyudmil Tsvetkov wrote:The game was already a white win: SF had been showing 105cps from the early mg, Houdini some 80cps. That is a win, however you would like to look at it.
So evaluating a position at +0.80 constitutes a win? This is new to me.
I for one don't think this is a rule that should be adopted.
SF quickly reached +1.05 and got stuck there:
[D]2r1r3/p2b1kbQ/1p1ppqp1/6P1/P2N4/1P2BP2/2P5/1K1R3R b - - 0 24
8 moves later H5 reached +0.77, which was the worst score it showed throughout the game:
[D]6r1/p4kbQ/1p4R1/3p1bP1/P7/1P6/K1r5/3R4 w - - 2 32

If +1.05 / +0.77 "proves" a win, then this proof was based on the 50-move rule being fully in force:
- the tree search of both engines know about the 50-move rule;
- the TBs they probe know about the 50-move rule.

So very clearly the scores shown by the engine are not at all proof of a win for white. Neither engine could possibly have known that a drawn 5-piece position was going to be adjudicated as win. They both knew very well that that 5-piece position was in fact a draw by the 50-move rule. Yet the game ended up in that position (with both engines correctly showing 0.00).

It is still possible that the position at, say, move 32 was a win for white when ignoring the 50-move rule, but the engine could not see that. The best we can do is run the position through SF with Syzygy50MoveRule set to false, which switches to the ICCF rule.

So I did that and the score gets stuck at +1.14. This suggests that since black cannot escape to a QvBB draw, it has to allow white slightly more space or something. But white still seems unable to make progress.

Code: Select all

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Even if white did have a winning position when ignoring the 50-move rule, the 50-move rule was in place and black made use of it, so black simply deserved to draw.

I wonder if without the adjudication, anyone would have considered the 50-move draw that would have been played out on the board to be unfair. (Actually, it would not have been played out as the TCEC draw rule would have kicked in long before.) To be honest, I do not wonder about this because I am sure that nobody would have seen anything unfair in it.

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Re: fortress_draw_rule

Post by zenpawn » Sat Nov 19, 2016 1:26 pm

Is there agreement among the Stockfish devs that it should have been a draw? If so, perhaps they could write the TCEC organizers and express their desire to have it scored the way both engines saw it.

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Re: fortress_draw_rule

Post by hgm » Sat Nov 19, 2016 1:31 pm

Why would it be relevant what the Stockfish devs think, or what the engines see? Since when is the score earned by a Chess game determined by what the players think, rather than what happens on the board?

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