Computer Chess Club Archives




Subject: Re: What to do with Horizon effect?

Author: Robert Hyatt

Date: 14:50:48 10/31/98

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On October 31, 1998 at 16:45:01, Inmann Werner wrote:

>I have problems with "nearly mate" positions, where the opponent can do some
>checks, so the mate gets beyond the horizon.
>One Example (really interesting!)
>Position (LCTII CMB 01)
>   xrxxxxkx
>   xqxxbpxx
>   xxxpxxpx
>   xxpPxxxx
>   PxNxxxxR
>   xxPxxQPx
>   xPxxxPKx
>   xxxxxxxx
>Best: c4d6/e7d6/f3f6 white wins
>In depth 7 , my program should find the solution, but it does not! The problem
>is, that black can make checks to bring the mate beyond the horizon. At each
>check, I extend the search for 1 ply, but it is not enough.
>The computer thinks:
>C4d6/e7d6/f3f6/b7d5+/g2h2/d6g3+!!/h2g3/d5d3+/g3h2/g8f8/    no h4h8 and black
>"stands good"
>7 plys plus 3 plys the checks end up at 10!!
>This things really often happen, and I am reall unhappy with it. When I tried to
>extend at a check with 2 plys, this problem was solved very early. But the
>overall searchdepth goes dramatically down, so the program plays worse.
>On an attack, it is nearly always possible for the opponent to slow down the
>attack with "senseless", but forced moves.
>I thought about something like:
>This is a mate in 1, therefore donĀ“t let you disturb with "senseless " moves.
>But I have no thought, how to implement such a thing.

not much you can do...  horizon effect happens anytime you stop the search
in a non-quiet position...  everybody sees it...  just get faster.. :)

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