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Subject: Re: Very curious Shredder 8 bug-confirmed

Author: William Penn

Date: 22:13:46 02/18/04

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On February 18, 2004 at 09:54:00, Mike Hood wrote:

>Shredder 8 gives the following information in "infinite analysis" mode, even
>though I have all the 3/4/5-piece tablebases.
>
>[D] 4k3/8/8/8/8/8/3q4/4K3 w - - 0 1
>
>Analysis by Shredder 8:
>
>1. = (0.00): 1.Kxd2
>2. = (0.00): 1.Kf1 Kf7
>
>We get a small clue what is happening, when we look at Fritz 8's analysis of the
>same position:
>
>Analysis by Fritz 8:
>
>1. = (0.00): 1.Kxd2
>2. -+ (-10.66): 1.Kf1 Kd7
>
>This is the analysis after 10 seconds. If I wait a few minutes Fritz finds a
>mate in 11. It looks like the tablebase engine goes on strike in positions which
>are a potential transition to K-K.

I verified your result with my Shredder 8 (CB GUI) installation, also that this
bug does not occur in other engines which I have available such as Shredder
7.04. So it is unique to Shredder 8. I also verified that it only happens if the
tablebases are active, so it is definitely a problem with tablebase
utilitization by Shredder 8.

I then played around a little... If you replace the Queen with a Rook, the same
thing happens. If you replace it with a knight or bishop, nothing happens -
Shredder 8 refuses to calculate anything whatsoever! I received a fatal system
exception when making these tests, closing the GUI automatically. I then
replaced the Queen with a Pawn, and discovered that it refuses to capture the
pawn. It doesn't even see that capturing move, so the problem may be more
serious than I originally thought. Again, these problems only happen with
tablebases active.
WP



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