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How to be sure it is draw ?



 
 
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  #1  
Old August 7th 03, 05:14 PM
JMR
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Default How to be sure it is draw ?

1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
Thanks


  #2  
Old August 8th 03, 01:23 PM
Claus-Jürgen Heigl
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Default How to be sure it is draw ?

JMR wrote:

1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
Thanks


Looks like a study, but I don´t know it. To win, White has to
free his knight out of the prison the Bb5 sets. Therefore White
has to manouvre such that his king can protect the knight moving
to one of the squares a6, c6, d7. Sacrificing the knight is not
an option because then the black white-squared bishop simply waits
until the pawn advances and then kills it. White can´t prevent this.

On the other hand Black can move the Bb5 only to give a check and
back again, otherwise the knight breaks out. So it is mainly the
task of the black king to keep the white king out.

If White wants his king to move towards the knight, he has to try
it on the kingside around the black king. There is no other way.

1. Kd2 Ke4

The white king somehow has to cross the g1-a7 diagonal, otherwise
he can´t make progress. The Bb5 controls the f1-a6 diagonal, so
White´s only squares to enter the g1-a7 diagonal are along the e1-b4
diagonal. Black´s king controls the g1-a7 diagonal from the h1-a8
diagonal.

2. Ke1 Kf3

Black still blocks the white king. Obviously 3. Kd2 Ke4 is just
repeating the position, so white has to resort to tempo moves.

3. Bc5 Kg2

For every square along the g1-a7 diagonal the white king threatens
to enter the black king has two corresponding squares along the
h1-a8 diagonal from where to block the white king. White can play
any tempo move he wants, Black simply oscillates on the two squares
his king has.

4. Kd2 Kf3 5. Kc3 Ke4

It should be obvious now that White has no means to force his king
on the h2-a7 diagonal. Therefore this is a draw.

Claus-Juergen
  #3  
Old August 8th 03, 06:30 PM
Hans Meier
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Default How to be sure it is draw ?

Sure it is draw. If black moves just the King between e4 and d5, there is
nothing White can do. White cannot attack the bishop on b5 and white cannot
move the pawn, so it will be draw by repetiton or 50-move rule.


1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
Thanks




  #4  
Old August 8th 03, 11:05 PM
JMR
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Default How to be sure it is draw ?

Thanks for your answer which is a demonstration.

Fritz gives 3.66 and never changes it's evaluation but I know this occurs in
a lot of positions.

JMR


"Claus-Jürgen Heigl" a écrit dans le message de
...
JMR wrote:

1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
Thanks


Looks like a study, but I don´t know it. To win, White has to
free his knight out of the prison the Bb5 sets. Therefore White
has to manouvre such that his king can protect the knight moving
to one of the squares a6, c6, d7. Sacrificing the knight is not
an option because then the black white-squared bishop simply waits
until the pawn advances and then kills it. White can´t prevent this.

On the other hand Black can move the Bb5 only to give a check and
back again, otherwise the knight breaks out. So it is mainly the
task of the black king to keep the white king out.

If White wants his king to move towards the knight, he has to try
it on the kingside around the black king. There is no other way.

1. Kd2 Ke4

The white king somehow has to cross the g1-a7 diagonal, otherwise
he can´t make progress. The Bb5 controls the f1-a6 diagonal, so
White´s only squares to enter the g1-a7 diagonal are along the e1-b4
diagonal. Black´s king controls the g1-a7 diagonal from the h1-a8
diagonal.

2. Ke1 Kf3

Black still blocks the white king. Obviously 3. Kd2 Ke4 is just
repeating the position, so white has to resort to tempo moves.

3. Bc5 Kg2

For every square along the g1-a7 diagonal the white king threatens
to enter the black king has two corresponding squares along the
h1-a8 diagonal from where to block the white king. White can play
any tempo move he wants, Black simply oscillates on the two squares
his king has.

4. Kd2 Kf3 5. Kc3 Ke4

It should be obvious now that White has no means to force his king
on the h2-a7 diagonal. Therefore this is a draw.

Claus-Juergen



  #5  
Old August 9th 03, 01:19 AM
Claus-Jürgen Heigl
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Default How to be sure it is draw ?

Hans Meier wrote:

Sure it is draw. If black moves just the King between e4 and d5, there is
nothing White can do. White cannot attack the bishop on b5 and white cannot
move the pawn, so it will be draw by repetiton or 50-move rule.


Not quite. As soon as the white king enters the g1-a7 diagonal,
Black is lost. Chess engines don´t recognize this because they think
Black is lost anyway. For example:

1. Kd2 Ke4 (1...Kd5?? 2. Ke3 loses even faster) 2. Ke1 Kd5?? 3. Kf2
Ke4 4. Kg3 Ke5 5. Kf3 Kf5 6. Ke3 Ke5 7. Bc5 Kd5 8. Kf4 Ke6 9. Ke4 Bf1
10. Bf2 Bb5 (or 10...Kd6 11. Bg3+ Ke6 12. Kd4 and Kc5) 11. Bg3 Bf1
12. Kd4 and Kc5.

Black has to block White from the g1-a7 diagonal. See my other post.

Claus-Juergen
  #6  
Old August 9th 03, 01:30 PM
Claus-Jürgen Heigl
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Default So Study from Gurvich refuted ?

JMR wrote:

The move 4.... Bc4 instead of 4....Nb3+ leads to the position
1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
given at the beginning of the thread and analysed as draw.
(4....Bc4 5.Kxc1 Bb5 6.Kb2 Kf6 7.Ke5)

Is it right ?


White can and should play 6. Kd2 Kf6 7. Ke3 and wins.

But I wonder what happens after 3...Na1 4. Kb2 Bc4 5. Nc6 Nb3
6. Kc3 Bd5 ?

Here Black doesn´t lose the knight. While the black knight can´t
get out he still blocks the white king while the black king can
come to help.

This is difficult to assess.

Claus-Juergen
  #7  
Old August 10th 03, 11:14 AM
Tobi Usher
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Default So Study from Gurvich refuted ?


"Claus-Jürgen Heigl" wrote


White can and should play 6. Kd2 Kf6 7. Ke3 and wins.

But I wonder what happens after 3...Na1 4. Kb2 Bc4 5. Nc6 Nb3
6. Kc3 Bd5 ?

Here Black doesn´t lose the knight. While the black knight can´t
get out he still blocks the white king while the black king can
come to help.

This is difficult to assess.

Claus-Juergen




In your last variation, instead of 4.Kb2, White plays 4.Nc6, followed by
5.Nd4, which is similar to the main line.
If 4...Nb3, then 5.Kb2 (or even 5.b5).

Tobi


  #8  
Old August 10th 03, 03:18 PM
Hans Meier
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Default How to be sure it is draw ?

To be 100% sure it is draw, someone could create a tablebase for KNBP vs. kb

1N6/8/1B6/1b2k3/1P6/2K5/8/8 w - - 0 8
Thanks




  #9  
Old August 10th 03, 03:22 PM
JMR
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Default So Study from Gurvich refuted ?

I do'nt understand
After 4.Nc6 4....Ce2+ whe have the position
8/6k1/1BN5/8/1P6/2K5/b3n3/8 w - - 0 5
which seems to be obvoulsy draw

"Tobi Usher" a écrit dans le message de
...

"Claus-Jürgen Heigl" wrote


White can and should play 6. Kd2 Kf6 7. Ke3 and wins.

But I wonder what happens after 3...Na1 4. Kb2 Bc4 5. Nc6 Nb3
6. Kc3 Bd5 ?

Here Black doesn´t lose the knight. While the black knight can´t
get out he still blocks the white king while the black king can
come to help.

This is difficult to assess.

Claus-Juergen




In your last variation, instead of 4.Kb2, White plays 4.Nc6, followed by
5.Nd4, which is similar to the main line.
If 4...Nb3, then 5.Kb2 (or even 5.b5).

Tobi




  #10  
Old August 10th 03, 06:16 PM
Claus-Jürgen Heigl
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Default So Study from Gurvich refuted ?

JMR wrote:

"Tobi Usher" a écrit dans le message de
...
In your last variation, instead of 4.Kb2, White plays 4.Nc6, followed by
5.Nd4, which is similar to the main line.
If 4...Nb3, then 5.Kb2 (or even 5.b5).


I do'nt understand
After 4.Nc6 4....Ce2+ whe have the position
8/6k1/1BN5/8/1P6/2K5/b3n3/8 w - - 0 5
which seems to be obvoulsy draw


I guess you got the third move wrong where I suggested 3...Na1
instead of 3...Nc1. Tobi is right, after 4. Nc6! the knight is lost.

My ideas behind 3...Na1 we

The white king blocks the diagonal a1-g7, so 4. Bd4+ won´t win the
knight (in the solution of Gurevich the king was on c1, so the threat
of Bd4 forced Black to Kf7).

The black king isn´t forced to f7, so later after the moves Black
Bc4 White Nc6 there isn´t the threat of Ne5+ winning the bishop.
Instead of Bd5 Black could play Nb3 rescuing the knight.

If White went immediately for the knight with the king (4. Kb2?)
Black plays 4...Bc4 5. Kxa1 (5. Nc6 Nb3) Bb5 setting up the draw
position because White can´t cross the a7-g1 diagonal with his
king.

Of course 4. Nc6! refutes this all.

All this exercise has one good thing: it helps understand the
seemingly weird move 6. Kc1 of Gurevichs solution.

1. Kd5 Nd2 2. Kd4 Nxb3 3. Kc3 Nc1 4. Kd2 (prevents the knight from
fleeing) 4...Nb3+ 5. Kc2 Na1+ 6. Kc1

If White played here 6. Kb2 this is the same position as after
3...Na1 4. Kb2. Black draws with 6...Bc4 7. Kxa1 Bb5.

After 6. Kc1 the threat of Bd4+ forces the black king to move away.
There are only 3 squares from where the black king reaches d5 or e4
in time after 7. Kb2 and 8. Kxa1, these are f6, f7, and g6. f6 does
nothing against Bd4+ and the others are really both of equal value.

After 6...Kf7 (or Kg6) 7. Kb2 Bc4 8. Nc6 (8. Kxa1? Bb5 =) Black
can´t play Nb3 because of Ne5+ winning the bishop. So 8...Bd5 9. Nd4
and the knight is finally caught.

What remains to check is if Black can blockade the pawns after
moves like 2...Bb1 or 2...Nf3+.

Claus-Juergen
 




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