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Subject: Re: I think I found a terrible bug in Tiger

Author: James T. Walker

Date: 14:50:15 03/23/01

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On March 23, 2001 at 14:35:06, Derek Mauro wrote:

>On March 23, 2001 at 01:09:23, James T. Walker wrote:
>
>>On March 23, 2001 at 00:49:45, James T. Walker wrote:
>>
>>>On March 22, 2001 at 17:55:07, Derek Mauro wrote:
>>>
>>>>I'm no expert on computer chess, but I thought I'd call this to everyone's
>>>>attention.  I was analyzing one of my recent games with Tiger (reg. and gambit),
>>>>and had a drawn position(I had black).
>>>>
>>>>[D]8/8/8/8/1n6/2K5/p7/6k1 w - - 0 111
>>>>
>>>>For some reason, in the obvious draw, Tiger gives it -12 and wants to play
>>>>Kxb4?? even after like 20 minutes.  All the programs seem to think its about -6
>>>>or so, but they all play the correct move, the obvious Kb2.  Is this a bug?
>>>>(The 4 piece tablebases will easily solve this bug, but this position is so
>>>>incredibly easy that I can't see why it would even need them.)
>>>>
>>>>This next position is also from the same game that all programs seem to have
>>>>trouble with, but I don't believe this is a bug.
>>>>
>>>>[D]8/1k6/2n5/8/6r1/p1K5/7R/8 b - - 0 87
>>>>
>>>>Most programs want to play Nb4, but from there white can force a draw.  I think
>>>>Ra4 is the correct move (Na5 might also work), but I'm not sure.  I also fell to
>>>>the tempation of Nb4 during the game :(
>>>>
>>>>Derek
>>>
>>>Hello Derek,
>>>Can you post a line which gives white the draw after Nb4?  It seems to me that
>>>black should still win this ending.  What am I missing?
>>>Jim
>>
>>This is funny.  The more I look at it the more I can't see how to win it either!
>>:-)
>>Jim
>
>The rest of the game went like this:
>87... Nb4 88. Rh7+ Ka6 89. Kb3 a2 90. Rh6+ Kb5 91. Rh5+ Kb6 92. Rh6+ Kc5 93.
>Rh5+ Kd4 94. Rh1 Kd3 95. Rd1+ Ke2 96. Rh1 Kd2 97. Rh2+ Ke3 98. Rh3+ Kf2 99. Rh1
>Rf4 100. Ra1 Ke2 101. Kc3 Re4 102. Rh1 Ke3 103. Re1+ Kf2 104. Ra1 Rg4 105. Kb3
>Ke3 106. Kc3 Ke2 107. Rh1 Ke3 108. Re1+ Kf2 109. Ra1 1/2-1/2
>
>Trading rooks on the 1st rank results in the position in the first diagram.  All
>those moves are pretty much forced.  There are a couple other moves in there,
>but none of them work (I think).  There is no way to trade rooks closer to the
>promotion square, I already tried that.  I think Ra4 was better, because it
>allows the knight to move and eventually attack the promotion square.
>Supporting a pawn from behind with a rook is also a basic principle.  Very tough
>endgame!

I worked on this a little while today with Fritz 6e..  This is what "we" came up
with.  1....Nb4 2. Rh7+ Kc6 3. Kb3 a2 4. Rh6+ Kd5 5. Rh1 Rh4 6. Rg1 Kc5 7. Rg5+
Kd4 8. Rg1 Rh8 9. Kb2 Ra8 10. Rd1+ Ke3 11. Ra1 Nd3 12. Kb3 Kd4 13. Kc2 Rb8  14
Kd2 Rb2+ & mate in 9  ..... 0-1

I think if Sune Larrson can post lines like this, then so can I.  :-)
I have no idea if this would really work or not so just consider it as a
"dream".
Jim



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