Rook Sacrifice with Horizon Effect

[Event ""]
[Site ""]
[Date "2009.2.1"]
[Round ""]
[White "?"]
[Black "?"]
[TimeControl "-"]
[Result "*"]

1.e4 e6 2.d4 d5 3.Nd2 Nf6 4.e5 Nfd7 5.f4 c5 6.c3 cxd4 7.cxd4 Nc6 8.Ngf3
f6 9.Bd3 fxe5 10.dxe5 Nc5 11.Bb1 Be7 12.a3 a5 13.h4 Qb6 14.Ng5 Kf8
15.Qh5 Bxg5 16.fxg5 Ke7 17.g6 h6 18.Rf1 Rg8 19.Rf7+ Ke8 *
r1b1k1r1/1p3Rp1/1qn1p1Pp/p1npP2Q/7P/P7/1P1N2P1/RBB1K3 w Q - 0 20
BR -- BB -- BK -- BR --
-- BP -- -- -- WR BP --
-- BQ BN -- BP -- WP BP
BP -- BN BP WP -- -- WQ
-- -- -- -- -- -- -- WP
WP -- -- -- -- -- -- --
-- WP -- WN -- -- WP --
WR WB WB -- WK -- -- --
I apologize for the crude diagram.

Modern engines in particular believe that Black is a bit better off here and they typically want to play 20.Qe2?. White however has a clear winning line after 20.Rxg7!, for example:

20.Rxg7 Rxg7 21.Qxh6 Rg8 22.Qh7 Ne7 23.Nf3 Kd7 24.Bg5 Re8 25.g7 Qd8 26.Bg6 Rg8 27.Rc1 b6 28.b4 axb4 29.axb4 Na6 30.Bd3 Nc7 31.Bxe7 Kxe7 32.Rxc7+ Qxc7 33.Qxg8 Qc1+ 34.Kf2 Qf4 35.Qh7 Ra2+ 36.Be2 Qf7 37.g8=Q 1-0

Crafty 20.14 finds the sacrifice in 5 minutes 26 seconds on my laptop.

Chessmaster 9000 SKR takes 18 minutes 22 seconds to find the sacrifice.

Slow Blitz Chess can't find it after a half hour.

Hope you don't mind me putting the diagram in properly dana : )



Modern engines in particular believe that Black is a bit better off here and they typically want to play 20.Qe2?. White however has a clear winning line after 20.Rxg7!, for example:

20.Rxg7 Rxg7 21.Qxh6 Rg8 22.Qh7 Ne7 23.Nf3 Kd7 24.Bg5 Re8 25.g7 Qd8 26.Bg6 Rg8 27.Rc1 b6 28.b4 axb4 29.axb4 Na6 30.Bd3 Nc7 31.Bxe7 Kxe7 32.Rxc7+ Qxc7 33.Qxg8 Qc1+ 34.Kf2 Qf4 35.Qh7 Ra2+ 36.Be2 Qf7 37.g8=Q 1-0

Crafty 20.14 finds the sacrifice in 5 minutes 26 seconds on my laptop.

Chessmaster 9000 SKR takes 18 minutes 22 seconds to find the sacrifice.

Slow Blitz Chess can't find it after a half hour.

Here is the complete game:




Edit: (posted 1st to see if everything was correct)

20.Rxg7 kind of leaps out of you - but could not analyse to that depth.
Would have gone for it OTB (I know me)
Then a chance I may have screwed it up (I know me).

What is the Horizon Effect in chess?
-GIN

Originally posted by Nowakowski
What is the Horizon Effect in chess?
-GIN

http://en.wikipedia.org/wiki/Horizon_effect

Originally posted by Nowakowski
What is the Horizon Effect in chess?
-GIN

When the sun sets over the horizon it gets dark,
you cannot see the pieces anymore so you go to bed and wait for sunrise.

Sunset usually happens once a day.

Originally posted by greenpawn34
When the sun sets over the horizon it gets dark,
you cannot see the pieces anymore so you go to bed and wait for sunrise.

Sunset usually happens once a day.

or you swindle someone into playing in a dark kitchen.
cheap!

-GIN

GM Larry Christianson has annotated two nice games in this opening in his "Attack with LarryC" video series with the ICC. Go to chess fm, go to "Attack with LarryC" archives and search "Trashing the Tarrasch"

Originally posted by Nowakowski
or you swindle someone into playing in a dark kitchen.
cheap!

-GIN

Ah ah - but the computer says it was not a swindle but a damn good move.

In a nutshell the horizon effect.

If the computer is only looking 4 ahead and there is a mate in 5
then it won't see it (obviously - it's horizon is set to 4).

So you play a move, it plays a move and suddenly it sees it.

That is when is it starts to to do all these silly moves to stop
the mate. Giving up it's Queen for check etc. etc.

I do recall a game years ago when a computer suddenly did this
and the stong players present and the programmers thought the
machine had broken down.

It turns out the computer had seen a mate (missed by all) and
this was it putting off the mate for as long as possible.

I'll try and dig out the position - it is most likely quite famous
in computer circles. The Box was Black, it was a Kingside fianchetto,
white checks on the back rank and the box blocks the check with
a Queen. That is all I can recall.

Originally posted by greenpawn34
Ah ah - but the computer says it was not a swindle but a damn good move.

In a nutshell the horizon effect.

If the computer is only looking 4 ahead and there is a mate in 5
then it won't see it (obviously - it's horizon is set to 4).

So you play a move, it plays a move and suddenly it sees it.

That is when is it starts to to do all these si ...[text shortened]... hecks on the back rank and the box blocks the check with
a Queen. That is all I can recall.

Duchess vs. Kaissa 1977


Black to move

Nobody around understood why Black played 1. ... Re8!? in this position. The answer was that after 1. ... Kg7, 2. Qf8+ mates in a few.

That's it.

I was close. it sacced a Rook for nothing not a Queen.
I got the fianchetto bit right though.

(not to bad considering it 31 years ago.)

The real scary thing is it does seem just like a few years ago.
Where did the 80' and 90'd go?

Cheers

I cked thatfirst position with my engine, and it indeed say Q-e2 after checking 330 milion positions