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Old June 18th 07, 02:43 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

I'm slowly downloading KBNNkr. The main reason I'm doing this is
because of a 1991 game between Karpov and Kasparov,
http://www.chessgames.com/perl/chessgame?gid=1067317.
This endgame occurs after white's 63rd move, and the end of the game
after move 114 has the same material. The position on move 63 is a
draw and the final position is a draw.

The main question I was wondering about, and the reason for
downloading KBNNkr, is if all of the intermediate positions were
drawn. Or perhaps did black make an error, but white didn't see the
win.

Perhaps someone knows the answer to that question. Anyone?
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Old June 18th 07, 05:49 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Jun 18, 2:43 pm, Jud McCranie
wrote:
I'm slowly downloading KBNNkr. The main reason I'm doing this is
because of a 1991 game between Karpov and Kasparov,http://www.chessgames.com/perl/chessgame?gid=1067317.
This endgame occurs after white's 63rd move, and the end of the game
after move 114 has the same material. The position on move 63 is a
draw and the final position is a draw.

The main question I was wondering about, and the reason for
downloading KBNNkr, is if all of the intermediate positions were
drawn. Or perhaps did black make an error, but white didn't see the
win.

Perhaps someone knows the answer to that question. Anyone?


You don't need to download the entire KBNNkr for that.
Just play through the moves of the game on the TB6 GUI at
http://www.k4it.de/index.php?topic=egtb&lang=en

Looks like it is perfectly drawn all the way through to me.

Regards,
Martin Brown

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Old June 18th 07, 06:16 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

Martin Brown wrote:

You don't need to download the entire KBNNkr for that.
Just play through the moves of the game on the TB6 GUI at
http://www.k4it.de/index.php?topic=egtb&lang=en

Looks like it is perfectly drawn all the way through to me.


As the site states that 5+1 tables are not online, and
considering that KBNNKR is 5+1, there still seems to be some
reason for downloading it.

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Old June 18th 07, 06:24 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Jun 18, 6:16 pm, Anders Thulin
wrote:
Martin Brown wrote:
You don't need to download the entire KBNNkr for that.
Just play through the moves of the game on the TB6 GUI at
http://www.k4it.de/index.php?topic=egtb&lang=en


Looks like it is perfectly drawn all the way through to me.


As the site states that 5+1 tables are not online, and
considering that KBNNKR is 5+1, there still seems to be some
reason for downloading it.


KBNNkr is 4+2

KBNNRk is 5+1 and few modern engines would have much trouble solving
for mate with or without perfect play.


Regards,
Martin Brown

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Old June 18th 07, 06:36 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Mon, 18 Jun 2007 09:49:58 -0700, Martin Brown
wrote:

You don't need to download the entire KBNNkr for that.


Right, but it would make it easier.

Looks like it is perfectly drawn all the way through to me.


That is what I suspected, but I didn't know. My followup question is
how hard is the defense?
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Old June 18th 07, 06:40 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Mon, 18 Jun 2007 10:24:42 -0700, Martin Brown
wrote:

KBNNRk is 5+1 and few modern engines would have much trouble solving
for mate with or without perfect play.


Some of the other 6-piece tablebases don't seem particularly useful
either - KQQQkn, etc.
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Old June 18th 07, 10:29 PM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Mon, 18 Jun 2007 09:49:58 -0700, Martin Brown
wrote:

Looks like it is perfectly drawn all the way through to me.


I did that (quite tedious) and white never had a win. Black almost
always had plenty of drawing moves, but there were opportunities to
step into a 29-move loss.
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Old June 19th 07, 10:21 AM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Jun 18, 6:36 pm, Jud McCranie
wrote:
On Mon, 18 Jun 2007 09:49:58 -0700, Martin Brown

wrote:
You don't need to download the entire KBNNkr for that.


Right, but it would make it easier.


I just managed to program the position into Freezer using my 5-men
tablebases and some crude approximations that cause certain moves
(that did not occur in the game) to be reported as lost (cutting down
the number of permutations that need to be considered. (eg. Force
black king to stay on ranks 6,7,8 & his R at the edge of the board and
f6). If he can hold a draw with those restrictions then it is up to
white to show a win.

It needed a database of 40M positions to encompass the entire game and
it showed it correctly as a draw. Took about 1h to get it right. OTOH
it took me 3 or 4 goes to replicate the 6 men TB results.

Initially I restricted the black K mobility too much and white found
an ingenious way of forcing the black K onto a forbidden black loses
square in the middle of the board. Takes a while to get used to making
Freezer do what you want. But it is handy for resolving tricky
endgames beyond the reach of conventional chess engines and TBs. It
gives more interesting results when there are blocked pawns still on
the board.

Programming it to reproduce known 6men TB results is how I am learning
to use it and gain confidence in the results (and understanding my
mistakes).

Looks like it is perfectly drawn all the way through to me.


That is what I suspected, but I didn't know. My followup question is
how hard is the defense?


Seems like the quick and easy heuristics of don't let the K + R get
forked or skewered is enough.
After that harassing the enemy king when it is safe to do so.

The only knife edge is the second last move where Ra6+ is necesary to
avoid the mate. A couple of times it is possible for black to lose by
very careless play earlier on but most sensibe moves were OK most of
the time.

Incidentally had it been KBBNkr the bishops and knights swapped blck
loses with mate in 52. The bishops deprive the R of too many safe
squares and there is a forcing line to a N fork on the R+K.

Regards,
Martin Brown

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Old June 20th 07, 12:18 AM posted to rec.games.chess.computer
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Default KBNNkr and Karpov-Kasparov 1991

On Tue, 19 Jun 2007 02:21:36 -0700, Martin Brown
wrote:

I just managed to program the position into Freezer using my 5-men


I've never heard of that program before.

Seems like the quick and easy heuristics of don't let the K + R get
forked or skewered is enough.


When i went through it, IIRC there were some 20+ move losses if black
put the rook on the g-file, or something like that. But I didn't look
into the winning line. The black rook harasses the bishop anytime it
can.

The only knife edge is the second last move where Ra6+ is necesary to
avoid the mate.


Yes, I think that was about the only time when black had only one
saving move. But Kasparov must have been aiming for that, since it is
a neater way to draw than claiming the 50-move (which he could have
done about the same time).

Incidentally had it been KBBNkr the bishops and knights swapped blck
loses with mate in 52. The bishops deprive the R of too many safe
squares and there is a forcing line to a N fork on the R+K.


I haven't investigated that, but "Secrets of Pawnless Endings" by John
Nunn says that KBBNkr is generally a win and KBNNkr is generally a
draw. There are some wins in KBNNkr that require 49 moves.
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