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Subject: Re: Bug in Fritz 8

Author: Uri Blass

Date: 07:06:28 12/31/02

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On December 31, 2002 at 09:58:28, Bob Durrett wrote:

>On December 31, 2002 at 09:33:06, Uri Blass wrote:
>
>>On December 31, 2002 at 09:01:55, Bob Durrett wrote:
>>
>>>In the following position, with Black to move, Fritz 8 says the correct move is
>>>Re8.  It gives a position evaluation of 0.00
>>>
>>>5r1k/pp1p2pp/n4q2/2pB4/2P2r2/8/PP2QPPP/R4RK1 b - - 0 18
>>>wKg1,Qe2,Bd5,Ra1,f1,Pa2,b2,c4,f2,g2,h2/bKh8,Qf6,Na6,Rf4,f8,Pa7,b7,c5,d7,g7,h7
>>>
>>>I forgot how to display the position here.  Maybe someone will do it for me.
>>>
>>>Bob D.
>>
>>Can you post the relevant game.
>
>I absolutely guarantee that you don't want to see the relevant game.  It was one
>of my 60+ blitz 2 12 ICC games which I played recently, after years of
>inactivity, for the purpose of determining how much my game had deteriorated.
>The game is filled with big errors on both sides.
>
>>
>>Maybe Re8 force repetition of the position so Fritz prefers repetition and not
>>negative evaluation(of course in that case white made an horrible blunder in a
>>previous move).
>
>If you will look at the position, you will see that there is no chance for a
>draw by repetition of the position.  But your idea does sound right.  Fritz must
>have gone into a mode where it "thought" there was a repetition of the position.
> Maybe there is an unintended jump to that "repetition of position display"
>subroutine or function which occurs improperly sometimes.
>
>
>>
>>A lot of programs evaluates first repetition as a draw.
>>It may be wrong in analysis but in games it is usually no problem.
>
>This jumped out at me in post-mortem analysis.  Strangely, my opponent in the
>actual game also played Re8?? and I, shamefully [!!!], failed to capture the
>rook.  Maybe this has something to do with the bug.

In that case it is not a bug because most programs are designed to assume that
second repetition is a draw in the analysis.

A bug is something that the programmer did not mean to happen.

I admit that there may be cases when it is not a draw but there are more
important things to improve than this problem that is not easy to solve in a
productive way(solutions may generate other problems like not seeing a draw by
repetition or not trying to make progress and often repeating a previous
position).

Uri



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