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Subject: Interesting search problem

Author: José Carlos

Date: 12:27:46 08/04/04

  In a test game, this position happened:

[D]3r4/6k1/P5p1/1PP2p2/2Qnrb1q/1B5P/5PP1/R2R3K w - - 3 40

  White, an old version of Shredder, was seing a7 here for some moves before,
with a plus score. At this point, at depth 11, it fails low on a7 (Qxf2 is very
strong then) and looks for another move. It chooses c6 with a plus score. Time
runs out and... c6??
  My impression is that Shredder was extending a7 (pawn to 7th), so it was
searching it a ply deeper than c6. But the refutation is the same!
  A possible solution for this is not allowing extensions for the moves in the
root position. Another solution: to force another iteration after the fail low
in the root (or the idea of Sune, IIRC, of doing a depth+1 null window search
for the new root move, but only after a fail low in the root). Or even forcing
the extensions for the non PV moves at the root if the PV move was extended and
failed low.
  Any experiences on the matter?

  José C.

Re: Interesting search problem John Merlino 15:17:52 08/04/04
Re: Interesting search problem Anthony Cozzie 14:59:25 08/04/04
Re: Interesting search problem Gerd Isenberg 13:43:31 08/04/04

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