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Subject: Re: Rebel XP - Many thanks Ed & odd test position

Author: Ed Schröder

Date: 15:37:52 07/23/02

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On July 23, 2002 at 18:29:34, Steve Maughan wrote:

>Many thanks to Ed for Rebel XP - you're too generous!
>
>I've been playing with the new package and it's fun.  I especially like the
>statistics that are shown as the engine searches.  However I was surprised by
>the following position:
>
>[d]r4qrk/ppp1b1pp/3p1p2/4pPPQ/4P2P/3PB3/PPP5/1K4RR w - -
>
>Key move Qxh7+ mate in 4.
>
>This is an old position from your tactics database and one that I actually sent
>to Ed way back in the days of ChessMachine, which couldn't solve the position in
>15 mins whereas THe King could solve it almost instantly.  Ed's obviously put it
>in with other problems and the last time I tested it on one of Ed's engines it
>was solved instantly.  To my amazement when I sparked up Rebel XP and set it to
>the combinations setting IT COULDN't SOLVE THE POSITION in 15 mins on my 1.5 GHz
>P4.  Strange! - heavy pruning I guess - or is it a search bug.  Interestingly
>without the Combinations option it is solved within 5 secs.
>
>Regards,
>
>Steve

Yep, this position has been bugging me since 1994 :)

The "combination" setting still uses the old search approach, too bad I have
forgotten to change that. For this version I only have focussed on the standard
(default) engine which does well in this position.

However withn a small parameter change in the "combination" settings it can be
fixed. If you are interested I can make the right personality for you.

Ed



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