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Subject: Prblem with EGTBs and Crafty?

Author: Bernhard Bauer

Date: 06:28:15 02/24/99


Hallo,
I came across a position from W. Chenkin,1960 in a book of J. Averbach.
Here is the position:

       +---+---+---+---+---+---+---+---+
    8  |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+
    7  |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+
    6  |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+
    5  |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+
    4  |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+
    3  |   |   |   |   |   |   | Q |   |
       +---+---+---+---+---+---+---+---+
    2  | K | *P|   |   |   | *R|   |   |
       +---+---+---+---+---+---+---+---+
    1  |   |   |   |   |   | *K|   |   |
       +---+---+---+---+---+---+---+---+
         a   b   c   d   e   f   g   h

FEN: 8/8/8/8/8/6Q/Kp3r/5k

For white to move Crafty gives:
White(1): end-game phase
              clearing hash tables
              time surplus   0.00  time limit 10:00 (10:00)
              depth   time  score   variation (1)
                1     0.13   1.80   1. Qe3
                1->   0.14   1.80   1. Qe3
                2     0.14   1.78   1. Qe3 Re2
                2     0.24     ++   1. Qd3+!!
                2     0.24  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
                2->   0.25  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
                3     0.25  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
                3->   0.28  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
                4     0.32  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
                4->   0.41  Mat51   1. Qd3+ Kg2 2. Qe4+ <EGTB>
              time=0.86  cpu=32%  mat=3  n=643  fh=85%  nps=747
              ext-> checks=101 recaps=0 pawns=0 1rep=4
              predicted=0  nodes=643  evals=72
              endgame tablebase-> probes done=135  successful=131  plimit=6
              hashing-> trans/ref=33%  pawn=99%  used=0%
              SMP->  split=0  stop=0  data=0/64  cpu=0.28  elap=0.86

mate in 51 moves.

This may be not enough to win due to the 50 moves rule.
When I do a search for the move that J. Awerbach gives in his book, Qg4!
Crafty gives some different output:

White(1): White(1): end-game phase
              clearing hash tables
              time surplus   0.00  time limit 10:00 (10:00)
              depth   time  score   variation (1)
                1     0.11   1.70   1. Qg4
                1->   0.11   1.70   1. Qg4
                2     0.11   1.68   1. Qg4 Rd2
                2->   0.11   1.68   1. Qg4 Rd2
                3     0.21     ++   1. Qg4!!
                3     0.24  Mat41   1. Qg4 Rd2 2. Qf4+ <EGTB>
                3->   0.24  Mat41   1. Qg4 Rd2 2. Qf4+ <EGTB>
                4     0.24  Mat41   1. Qg4 Rd2 2. Qf4+ <EGTB>
                4->   0.24  Mat41   1. Qg4 Rd2 2. Qf4+ <EGTB>
              time=0.69  cpu=20%  mat=3  n=275  fh=82%  nps=398
              ext-> checks=69 recaps=0 pawns=0 1rep=0
              predicted=0  nodes=275  evals=69
              endgame tablebase-> probes done=62  successful=62  plimit=7
              hashing-> trans/ref=32%  pawn=99%  used=0%
              SMP->  split=0  stop=0  data=0/64  cpu=0.14  elap=0.69

mate in 41 moves.

This would suffice for a win.
So may question is simply weather Crafty could be improved in that area.

Kind regards
Bernhard



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