[net.games.chess] problem

ken@alice.UucP (Ken Thompson) (09/09/85)

 
White to move: Adjudicate!
WK-c7
WP-d5
BK-d4
BB-a7
BB-a8

Submitted on behalf of A. J. Roycroft
(editor of EG magazine.)

dpb@philabs.UUCP (Paul Benjamin) (09/10/85)

> White to move: Adjudicate!
> WK-c7
> WP-d5
> BK-d4
> BB-a7
> BB-a8
> 
> Submitted on behalf of A. J. Roycroft
> (editor of EG magazine.)

1. d6 is forced, else lose the pawn and the game

1. ... Kc5
2. d7  Bb6+
if 3. Kb8  Be4
   4. Kc8  Bf5 wins

so 3. Kc8  Kc6
   if 4. d8=Q Bb7+
      5. Kb8  Bxd8 wins

   so 4. d8=N+

Without my ending books handy, I'm just winging this response
(I've never seen K+2B vs. K+N). It seems to me that White draws 
this position, but I'm not totally sure. For instance, if 
4. ... Kd6 5. Nb7+ Kc6 6. Nd8+ or 4. ... Kd6 5. Nb7+ K(other than c6) 
6. Kb8 draws. If Black's king goes around to a6 instead, then White's 
king gets away from the edge. 

larry@cca.UUCP (Laurence Schmitt) (09/10/85)

> 
>  
> White to move: Adjudicate!
> WK-c7
> WP-d5
> BK-d4
> BB-a7
> BB-a8
> 
> Submitted on behalf of A. J. Roycroft  [by Ken Thompson]
> (editor of EG magazine.)

Don't look further if you don't want my answer...











My analysis says it's a draw:

	1. d6	Kc5
	2. d7	Bb6+
	3. Kc8	Kc6
	4. d8=N+!

The key move.  If instead 4. d8=Q, Black wins with 4...Bb7+ 5. Kb8 B:d8.

I'm not sure what the general case is of 2 B's vs. a N (i.e., whether or not
there are any tricks for the weaker side to beware), but the given position 
is completely drawn because of the plight of the Black B on a8:

	Try 4...Kd6 5. Nb7+ Kc6 (or 5...K other 6. Kb8) 6. Kb8 and Black 
	either stalemates or loses his B.  Similarly 4...Kb8 5. Nb7 Ka6 6. Kb8!

						-Larry Schmitt

halle@hou2b.UUCP (J.HALLE) (09/13/85)

How about    1. ...  Bc5
Now black will win the pawn but lose the bishop, bringing
the ending to one bishop vs. nothing.  Again a draw.

ken@alice.UucP (Ken Thompson) (11/11/85)

belle's first problem:

WK ??
WQ c5
WN c6
BK c8
BQ c7

place the WK anywhere and then white-to-move.
white to win.

with some help from AJ Roycroft and K Thompson.

ken@alice.UucP (Ken Thompson) (11/19/85)

belle's second composition:
	WK b8
	WQ e8
	WR b5
	BK a6
	BQ f6

this is a VERY unique position, why?