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Tablebases and the rule of 50 moves



 
 
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  #1  
Old August 21st 03, 08:48 AM
JMR
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Default Tablebases and the rule of 50 moves

In the posiotion 8/1k6/8/3KB1N1/8/8/5n2/8 w - - 0 1 The Tablebases annouce
correctly mate in 85 moves. But strangely they stop to work after 50 moves
certainly because of the rule of the 50 moves. To have the end one's have to
copy the position in anoter board, finish it and then cut and paste.
It think it's strage !


  #2  
Old August 21st 03, 08:48 PM
CeeBee
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Default Tablebases and the rule of 50 moves

"JMR" wrote in rec.games.chess.computer:

In the posiotion 8/1k6/8/3KB1N1/8/8/5n2/8 w - - 0 1 The Tablebases
annouce correctly mate in 85 moves. But strangely they stop to work
after 50 moves certainly because of the rule of the 50 moves. To have
the end one's have to copy the position in anoter board, finish it and
then cut and paste. It think it's strage !



Most if not all chess programs use the FIDE rules. Until recently the FIDE
had some exceptions to the 50 move rule in cases like king and pawn
against king and two knights, but eventually ruled that no matter what the
solution is - the rule is that after 50 moves - no captures no pawn moves
- the game is a draw.

Again: it has nothing to do with the _theoretical_ solution available, but
simply to the rules we agreed to. So your program is right and it's not
strange: in chess it isn't a mate in 85 moves, it's a draw because you
can't mate the opponent before the 50 move rule comes into play.

What you're doing is like wondering how long it takes for team a to win or
lose with 10-0 from team b in soccer: it could take an hour, it could take
five days, but the rules limit the game to 90 minutes, and at the end of
the 90 minutes that's the score.

Of course I can understand that you want to see the mating sequence, but
the program is still right if it cuts off after 50 moves.

--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


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  #3  
Old August 21st 03, 08:54 PM
CeeBee
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Default Tablebases and the rule of 50 moves

CeeBee wrote in rec.games.chess.computer:

Of course I can understand that you want to see the mating sequence,
but the program is still right if it cuts off after 50 moves.



BTW if you are using a Fritz GUI program the draw window will pop up a few
times; if you click it away during these few moves it will stay away and
let you end the mating sequence without interruption.

Under ChessBase 8 it's no problem at all: no claims, just playing to the
end. Load Tabelbase 2.0 and play out the sequence. This was all done in
one stint:

1.Bc3 Kc8 2.Nf7 Nd3 3.Kc6 Nf4 4.Bf6 Nd3 5.Nd6+ Kb8 6.Kb6 Nf4 7.Be5 Ng6
8.Bh2 Ne7 9.Nf5+ Ka8 10.Nd4 Nf5 11.Nb5 Nd4 12.Nc7+ Kb8 13.Ne6+ Ka8 14.Nc5
Nc2 15.Na4 Ne3 16.Ka6 Nd5 17.Bd6 Nc7+ 18.Kb6 Nd5+ 19.Kc6 Ne3 20.Bc5 Nf5
21.Kc7 Nh4 22.Nc3 Ng2 23.Kc6 Ne1 24.Nd5 Kb8 25.Be3 Nd3 26.Ne7 Ne5+ 27.Kd5
Nd7 28.Kd6 Nf6 29.Bd4 Nh7 30.Kc6 Ng5 31.Kb6 Ka8 32.Be5 Nf3 33.Bf4 Ne1
34.Nd5 Ng2 35.Bg5 Ne1 36.Bh4 Nd3 37.Bg3 Nb4 38.Nc7+ Kb8 39.Kc5 Nc2 40.Nb5+
Kb7 41.Nd6+ Ka6 42.Nc4 Ka7 43.Bf4 Ne1 44.Ne5 Ng2 45.Bg5 Kb7 46.Nd3 Ka6
47.Nb4+ Ka5 48.Nc2 Ka4 49.Kc4 Ka5 50.Kd3 Kb5 51.Ke2 Ka4 52.Nd4 Kb4 53.Nf5
Kc4 54.Kf2 Kd5 55.Kxg2 Ke5 56.Ne7 Ke4 57.Kg3 Ke5 58.Kf3 Kd4 59.Kf4 Kc4
60.Ke4 Kb5 61.Kd5 Kb6 62.Bf4 Kb7 63.Kc5 Ka6 64.Nd5 Ka7 65.Kc6 Ka8 66.Be3
Kb8 67.Nc7 Kc8 68.Ba7 Kd8 69.Nd5 Ke8 70.Bd4 Kf7 71.Nf4 Ke7 72.Kc7 Ke8
73.Bf2 Kf7 74.Bh4 Ke8 75.Kd6 Kf7 76.Bg5 Ke8 77.Ke6 Kf8 78.Nh5 Ke8 79.Ng7+
Kf8 80.Kf6 Kg8 81.Ne6 Kh7 82.Kf7 Kh8 83.Bf4 Kh7 84.Nf8+ Kh8 85.Be5#



--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

  #4  
Old August 22nd 03, 10:08 PM
Ѥ
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Default Tablebases and the rule of 50 moves

Keep in mind also that the 50 move rule only applies when 50 moves transpire
WITHOUT a pawn push or a piece capture.


"JMR" wrote in message
...
In the posiotion 8/1k6/8/3KB1N1/8/8/5n2/8 w - - 0 1 The Tablebases annouce
correctly mate in 85 moves. But strangely they stop to work after 50 moves
certainly because of the rule of the 50 moves. To have the end one's have

to
copy the position in anoter board, finish it and then cut and paste.
It think it's strage !




  #5  
Old August 24th 03, 12:21 PM
Joerg Moormann
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Default Tablebases and the rule of 50 moves

What you're doing is like wondering how long it takes for team a to win or
lose with 10-0 from team b in soccer: it could take an hour, it could take
five days, but the rules limit the game to 90 minutes, and at the end of
the 90 minutes that's the score.

Of course I can understand that you want to see the mating sequence, but
the program is still right if it cuts off after 50 moves.



Hi,

sorry, IMHO I should get the chance to win the game if the position is
won. If this is not possible the rules are bad and must be changed.

On the other hand, if I agree that the game is draw after 50 moves, if
I can win or not, then the tablebases are wrong. They give a win in
85. But it is not won. It is draw. Thus the TB should say "draw".

That brings another question. Ken Thompen (KT) base gives a win in the
given position in 55 moves. KT calculates not to mate, it calculates
to the next minor-men-position, i. e. KBN-K

What, if I could 10 or 20 moves later choose a side-line, which is not
the best (according to the TB, because it needs more moves), but which
would lead to a win of the knight - in less than 50 moves? Including
mate it might be 87 or 88 moves. Then the position was won. But the
tablebases cannot give me an answer to that question.

In the give position KT disagrees with your tablebases. It says:

46.Sf3 ( 9) Kc8 ( 9)
47.Kd5 ( 8) Kd7 ( 8)
48.Ld2 ( 7) Kc7 ( 7)
49.Se5 ( 6) Kd8 ( 6)
50.Ke4 ( 5) Ke7 ( 5)
51.Lg5 ( 4) Kf8 ( 4)
52.Sd3 ( 3) Kg7 ( 3)
53.Kf3 ( 2) Kg6 ( 2)
54.Ld8 ( 1) Kh7 ( 1)
55.Kg2 ( 21)

46. Nd3 needs 10 moves (to win the knight) and and 46... Ka6 is not
good. Better is 46... Kc7.

After all: 55 moves is still 5 to much, but there are situations,
where the game is won and the Nalimovs come to a wrong result.

Greetings
Joerg
  #6  
Old August 24th 03, 12:26 PM
Joerg Moormann
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Default Tablebases and the rule of 50 moves

46.Sf3 ( 9) Kc8 ( 9)
47.Kd5 ( 8) Kd7 ( 8)
48.Ld2 ( 7) Kc7 ( 7)
49.Se5 ( 6) Kd8 ( 6)
50.Ke4 ( 5) Ke7 ( 5)
51.Lg5 ( 4) Kf8 ( 4)
52.Sd3 ( 3) Kg7 ( 3)
53.Kf3 ( 2) Kg6 ( 2)
54.Ld8 ( 1) Kh7 ( 1)
55.Kg2 ( 21)


Sorry, S = knight, L = bishop (its German).
  #7  
Old August 24th 03, 03:55 PM
CeeBee
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Default Tablebases and the rule of 50 moves

Joerg Moormann wrote in rec.games.chess.computer:

sorry, IMHO I should get the chance to win the game if the position is
won. If this is not possible the rules are bad and must be changed.



How will you find out? A referee with a PC checking if it's a forced mate
and see if your opponent mates you in exactly 85 moves? And when will you
start checking that? When you offer a draw and your opponent refuses it
just to have his position checked to see if there's a forced mate?

And what if he continues and doesn't succeed? If he misses a move and it's
move 86 - and it's mate in three moves now? Will he be allowed to continue
playing? And what if he misses again and it's move 90 and now it's forced
mate in 6 moves? Will he be allowed to continue playing? And what if he
misses the move in six but shows another mate in 8?

I understand your point but you confuse a _technical_ solution with a
_gaming_ solution. It might also be possible to win a game after a
threefold repetition. Because it's still a technical win one should
continue?

I agree with you that rules never should be fixed for eternity, but I
think the FIDE decision is a right one: without a computer no one would
have found this a mate in 85in an actual game. And to prevent just those
dreadfully long sessions to find out in a real game, exactly for that
reason the 50 move rule was introduced.




--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

  #8  
Old August 24th 03, 04:34 PM
Joerg Moormann
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Default Tablebases and the rule of 50 moves

I agree with you that rules never should be fixed for eternity, but I
think the FIDE decision is a right one: without a computer no one would
have found this a mate in 85in an actual game. And to prevent just those
dreadfully long sessions to find out in a real game, exactly for that
reason the 50 move rule was introduced.



Yes, I agree with you absolutely. Its a very theoretical discussion.
In practical play there is no human that can win such a position. Not
even in 20 moves.

But the threefold repetition is a bad comparsion. I think the idea of
this rule is, if both players have no idea how to continue, the game
must be draw. And its my decission if I repeat or not.

The idea of the 50-moves-rule is IMHO, that a game shouldnt be won by
exceeding time - moving and moving without any plan.

So in OTB chess the 50-move-rule is a good rule, but unfortunately not
in corr-chess. Luckily I have never had such a position in my corr
games to this day :-)

Greetings
Joerg
  #9  
Old August 24th 03, 08:08 PM
Dieter Buerssner
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Default Tablebases and the rule of 50 moves

Joerg Moormann wrote:

That brings another question. Ken Thompen (KT) base gives a win in the
given position in 55 moves. KT calculates not to mate, it calculates
to the next minor-men-position, i. e. KBN-K

What, if I could 10 or 20 moves later choose a side-line, which is not
the best (according to the TB, because it needs more moves), but which
would lead to a win of the knight - in less than 50 moves?


It is impossible, in this case, because of the way Thompson TBs are
calculated. When the position is pawnless, you can trust the distance to
conversion (DTC) that Thompson TBs say. This is the way, they are
calculated - the loser side tries to avoid the conversion as long as he
can, and the winner side tries the opposite. Thompson TBs in general will
not yield in the shortest mate. The case is different for Nalimov TBs.
One may find similar positions, where Nalimov TBs announce a mate in 85,
and Thompson DTC shows 49 (so enough to win). It could be, that the info
the Nalimov TB includes would however yield in a draw (and perhaps, to
avoid the draw with the Tompson TB would yield in a longer mate).

In the more general case with pawn(s) on the board, the info Tompson TBs
show will still be not enough. I am working at the moment at TBs, that
will include the 50 moves rule. For this, I consider a pawn push as a
"conversion". When more than 50 moves are needed until a pawn push or a
capture, the TB generating algorithm will see, that the position is a
draw.

After all: 55 moves is still 5 to much, but there are situations,
where the game is won and the Nalimovs come to a wrong result.


Yes. It will happen only very rarely in practical games however. Likely
candidates where this can happen are KNNKP, KQPKQ and KBBKN.

Regards,
Dieter
  #10  
Old August 24th 03, 09:22 PM
Bo Persson
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Default Tablebases and the rule of 50 moves


"CeeBee" skrev i meddelandet
Most if not all chess programs use the FIDE rules. Until recently

the FIDE
had some exceptions to the 50 move rule in cases like king and pawn
against king and two knights, but eventually ruled that no matter

what the
solution is - the rule is that after 50 moves - no captures no pawn

moves
- the game is a draw.


The 50 move rule was actually the original rule.

It was not until computers started to show longer mate lines that the
rules were modified so that, for some specific endings, mate was not
declare until after 65 (or perhaps even more) moves. After trying this
for some years, and finding even longer mate sequences for other
endings, it was decided to be of now advantage at all. I guess the
main problem is that even if a computer can find a forced mate in 65
or 85, no human player can ever play it out correctly.

The only result is long and *boring* endgames, where the players would
agree on a draw just to get out of it. In a tournament, an extra hour
or two of sleep can get you this half point back the next day anyway.


Bo Persson

 




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