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Subject: What to do with Horizon effect?

Author: Inmann Werner

Date: 13:45:01 10/31/98


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.
Suggestions?

Werner








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