Author: Robert Hyatt
Date: 10:49:17 09/22/99
Go up one level in this thread
On September 22, 1999 at 02:53:30, Ricardo Gibert wrote:
>On September 21, 1999 at 09:59:01, Robert Hyatt wrote:
>
>>On September 20, 1999 at 18:36:42, Howard Exner wrote:
>>
>>>On September 20, 1999 at 14:42:27, Robert Hyatt wrote:
>>>
>>>>
>>>>Here are a couple of examples:
>>>>
>>>> +---+---+---+---+---+---+---+---+
>>>> 8 | | | | | | | *K| |
>>>> +---+---+---+---+---+---+---+---+
>>>> 7 | *P| *P| | | | *P| *P| *P|
>>>> +---+---+---+---+---+---+---+---+
>>>> 6 | | | | | | | | |
>>>> +---+---+---+---+---+---+---+---+
>>>> 5 | | | | | | | | |
>>>> +---+---+---+---+---+---+---+---+
>>>> 4 | | | | | | | | |
>>>> +---+---+---+---+---+---+---+---+
>>>> 3 | | | | | | | P | |
>>>> +---+---+---+---+---+---+---+---+
>>>> 2 | P | P | P | | | | P | |
>>>> +---+---+---+---+---+---+---+---+
>>>> 1 | | | | | | | K | |
>>>> +---+---+---+---+---+---+---+---+
>>>> a b c d e f g h
>>>>
>>>>
>>>>(fen 6k1/pp3ppp/8/8/8/6P1/PPP3P1/6K1/ w)
>>>>
>>>>old (16.18 crafty) evaluates this as -36 (black is better) because of
>>>>those two doubled kingside pawns. new crafty says +.36 because white has
>>>>a potential outside passer on the c file, black can't force a passer without
>>>>the king helping. Better...
>>>
>>>Black can force a passer here without the king's help.
>>>
>>
>>Of course but he also gives black one in return, which was the point. My
>>eval doesn't give anyone credit here. But the search returns a mate in 14
>>almost instantly. (mate in 14 for black winning)
>
>
>I think you got the colors mixed up above. BTW could you post the mate in 14?
>
>
I think the mate in 14 was with the 'contrived' position and not the one I
posted. IE the one with the white king hemmed in on the queenside and
totally locked in by the bishop/pawns... It was a simple win for black as
the passer was totally unstoppable and queened (and mated) before white's
passer could do any damage...
>>
>>Remember, I am simply trying to recognize (positionally) winning positions. I
>>don't think it is physically possible to force crafty into such a position with
>>the king totally blocked behind a bishop that is totally blocked, etc. I'll
>>accept that kind of error to get the real positions mostly right. :)
>>
>>Even an outside passed pawn doesn't always win. But it does most of the time,
>>so that the eval term I have had for years has always been pretty accurate...
>>
>>
>>
>>>Try the below artificial (and illegal) example on crafty. It will test
>>>whether black can force a passer without the king's help. It has that same pawn
>>>configuration on the king's side.
>>>
>>>1kb5/1p1p1ppp/1P1P4/8/8/1p1p2P1/1P1P2P1/K1B5 w
>
>The position appears legal to me. Perhaps you left off W: Pa3; B: Pa6?
>
>With white or black to move black wins (You can start the white K on b1 if you
>like. It makes no difference.). Black temporizes if necessary to make sure the
>white K is on a1 before sacrificing a pawn, then since he Qs 1st Qxc1 will mate.
>Note black does not even need the mate if he moves first. After h5 he will have
>2 tempos to spare.
>
>>
this is the mate in 14 position (black winning)
here is the output...
24-> 1.14 -9.60 1. g4 f6 2. Kb1 g6 3. Ka1 h5 4. gxh5
gxh5 5. Kb1 f5 6. Ka1 f4 7. Kb1 h4
8. Ka1 h3 9. gxh3 f3 10. Kb1 f2 11.
Ka1 f1=Q 12. Kb1 Qxh3 <HT>
25 1.16 -- 1. g4
25 1.39 -Mat14 1. g4 f6 2. Kb1 g6 3. Ka1 h5 4. gxh5
gxh5 5. Kb1 h4 6. Ka1 f5 7. Kb1 f4
8. Ka1 h3 9. gxh3 f3 10. Kb1 f2 11.
Ka1 f1=Q 12. Kb1 Qd1 13. h4 Qc2+ 14.
Ka1 Qxc1#
25-> 1.42 -Mat14 1. g4 f6 2. Kb1 g6 3. Ka1 h5 4. gxh5
gxh5 5. Kb1 h4 6. Ka1 f5 7. Kb1 f4
8. Ka1 h3 9. gxh3 f3 10. Kb1 f2 11.
Ka1 f1=Q 12. Kb1 Qd1 13. h4 Qc2+ 14.
Ka1 Qxc1#
the times are in seconds. On my quad xeon...
>>
>>if you try to win the position I originally gave, if anybody wins, white
>>wins, and white winning is pretty likely. Because my first moves as white
>>will not have to worry about a black pawn running in, since the white king
>>will stop it easily.
>
>I'm pretty sure it's a draw. Black must wait patiently before "coming alive" on
>the K-side. It is also important to keep at least one black pawn on the Q-side,
>though in some variations, it is not a necessity. With black to move, the draw
>is definite.
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