Author: Gerd Isenberg
Date: 11:33:00 08/25/04
Go up one level in this thread
On August 25, 2004 at 14:01:38, Volker Böhm wrote: >On August 25, 2004 at 13:54:27, Stan Arts wrote: > >>On August 25, 2004 at 13:41:18, Volker Böhm wrote: >> >>>On August 25, 2004 at 13:06:40, Álvaro Begué wrote: >>> >>>>On August 25, 2004 at 12:52:46, Volker Böhm wrote: >>>> >>>>> >>>>>Hi, >>>>> >>>>>the following position of the iq - test (position 166) cannot be solved from >>>>>spike in reasonalbe time (> 2h): >>>>> >>>>>[D]r4r1k/6pp/3p3b/1p1Npb2/3nB2q/2N3P1/PP3P1P/R2Q1RK1 b - - 0 1 >>>>> >>>>>(The move to find is Qxe4) >>>>> >>>>>The reason is a nullmove-problem. After the queen-sac there are many moves that >>>>>leads to a mate-thread. But one queen back spike tends to prune because of >>>>>nullmove result. >>>>> >>>>>I tested the position with fritz 8, he solves it in 8 ply in nearly no time. >>>>>(PRODEO NEEDS 7 Ply, Ruffian 1.01 11 Ply). >>>>> >>>>>Are there non commercial engines that solves this position too in a short amount >>>>>of time? >>>>>Maybe the author of this engine would be so kind to explain the rule that solves >>>>>the nullmove-problem. >>>>> >>>>>Thanks Volker >>>> >>>>Ruy-Lopez solves it in depth 8, in under 30 seconds. >>> >>>Do you know if Ruy-Lopez has a special rule to skip nullmove-prunings in such a >>>position? >>> >>>Greetings Volker >> >>But this position seems very dependant on static evaluation. Have you tried >>forcing Qxe4 to see if Spike really doesn't see it, or just prefers another >>move instead, that it scores slightly better. (The program needs to score >>mobility and pressure on the king and so considerably, I guess. Before it'll >>choose Qxe4) There seems no clear short-term tactical win. (is there?) >> >>Greetings and goodluck >>Stan > >Thanks for the hint. You are right. Spike does not score pressure on the king >very much if no queen is present. On top the queen has a high score (960 cp). >Reducing the score of the queen solves the position. > >Thus no "fault" of the search. As this is the only position in iq-test spike >does not solve in less than 10 minutes I thought I had found a "hole" in search. > >Greetings Volker Queen and passer against three light pieces - a bit uncertain without further positional considerations. There might be a lot of cases where white is winning with this material ;-) The huge black f3 bishop controlling the whole a1-h8 diagonal, the bishop pair, active knight (oups attacked, anyway), safe black king, the passive white f1-rook, weak, attacked pawns. That and counting weighted attacks and dominated squares should clearly favour black here. [D]5r1k/6pp/3p3b/4p3/2Qn4/r1P2bP1/P4P1P/4RRK1 b - - Gerd
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