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Subject: Re: Fine #70 and hash bug(s) (warning: long post)

Author: Martin Giepmans

Date: 09:40:19 04/19/04

Go up one level in this thread


On April 19, 2004 at 11:43:59, Uri Blass wrote:

>On April 18, 2004 at 19:56:25, Andrew Wagner wrote:
>
>>     Ok, I've been banging my head against this one all day. This is Fine #70:
>>[d]8/k7/3p4/p2P1p2/P2P1P2/8/8/K7 w - -
>>
>>     Below is Trueno's output for the position. Of course, the correct result is
>>+1.8 (Trueno counts pawns as .9) with the best move of Kb1. It finds that but
>>then changes its mind. I've been told that this position is generally infamous
>>for catching hash bugs. Anyone have any suggestions how to attack this one? Null
>>move is off, and I'm evaluating material only, using a single replace-always
>>hash table. Any suggestions would be VERY much appreciated). Andrew
>>
>>           -------------------------------
>>        8 | . | . | . | . | . | . | . | . |
>>          |-------------------------------|
>>        7 | k | . | . | . | . | . | . | . |
>>          |-------------------------------|
>>        6 | . | . | . | p | . | . | . | . |
>>          |-------------------------------|
>>        5 | p | . | . | P | . | p | . | . |
>>          |-------------------------------|
>>        4 | P | . | . | P | . | P | . | . |
>>          |-------------------------------|
>>        3 | . | . | . | . | . | . | . | . |
>>          |-------------------------------|
>>        2 | . | . | . | . | . | . | . | . |
>>          |-------------------------------|
>>        1 | K | . | . | . | . | . | . | . |
>>           -------------------------------
>>            A   B   C   D   E   F   G   H
>>
>>Fifty: 0  En Passant: 0
>>Castle: 0000
>>Ply: 0  To move: True
>>
>>
>>1. Score: .9; Time: 0; nodes: 4; PV: a1-b2
>>2. Score: .9; Time: 0; nodes: 15; PV: a1-b2 a7-b6
>>3. Score: .9; Time: 0; nodes: 48; PV: a1-b2 a7-b6 b2-c3
>>4. Score: .9; Time: 0; nodes: 111; PV: a1-b2 a7-b6 b2-c3 b6-c7
>>5. Score: .9; Time: 0; nodes: 231; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4
>>6. Score: .9; Time: 0; nodes: 408; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>7. Score: .9; Time: 0; nodes: 671; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7 c4-d3
>>8. Score: .9; Time: 0; nodes: 1003; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7
>>9. Score: .9; Time: 0; nodes: 1443; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4
>>10. Score: .9; Time: 0; nodes: 1968; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7
>>11. Score: .9; Time: 0; nodes: 2735; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3
>>12. Score: .9; Time: 0; nodes: 3522; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7
>>13. Score: .9; Time: 0; nodes: 4416; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4
>>14. Score: .9; Time: 1; nodes: 5410; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7
>>15. Score: .9; Time: 1; nodes: 6584; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3
>>16. Score: .9; Time: 1; nodes: 7885; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7
>>17. Score: .9; Time: 1; nodes: 9273; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4
>>18. Score: .9; Time: 1; nodes: 10845; PV: a1-b2 a7-b6 b2-c3 b6-c7 c3-c4 c7-d7
>>c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7
>>19. Score: .9; Time: 1; nodes: 16249; PV: a1-b2 a7-b6 b2-c3 b6-b7 c3-c4 b7-b6
>>c4-d3 b6-c7 d3-c4 c7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3
>>20. Score: .9; Time: 1; nodes: 18816; PV: a1-b2 a7-b6 b2-c3 b6-b7 c3-c4 b7-b6
>>c4-d3 b6-c7 d3-c4 c7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3 d7-e7 d3-c4 e7-d7 c4-d3
>>d7-e7
>>21. Score: 1.8; Time: 2; nodes: 30305; PV: a1-b1 a7-b6 b1-c2 b6-b7 c2-d2 b7-c7
>>d2-d3 c7-b6 d3-e3 b6-c7 e3-f3 c7-d7 f3-g3 d7-e7 g3-h4 e7-f6 h4-h5 f6-f7 h5-g5
>>f7-e8 g5-f5
>>22. Score: 1.8; Time: 2; nodes: 40127; PV: a1-b1 a7-b6 b1-c2 b6-b7 c2-d2 b7-c7
>>d2-d3 c7-b6 d3-e3 b6-c7 e3-f3 c7-d7 f3-g3 d7-e7 g3-h4 e7-f6 h4-h5 f6-f7 h5-g5
>>f7-e8 g5-f5 e8-e7
>>23. Score: 1.8; Time: 2; nodes: 50869; PV: a1-b1 a7-b6 b1-c2 b6-b7 c2-d2 b7-c7
>>d2-d3 c7-b6 d3-e3 b6-c7 e3-f3 c7-d7 f3-g3 d7-e7 g3-h4 e7-f6 h4-h5 f6-f7 h5-g5
>>f7-e8 g5-f5 e8-e7 f5-e4
>>24. Score: 1.8; Time: 3; nodes: 64039; PV: a1-a2 a7-b6 a2-b3 b6-c7 b3-c3 c7-b6
>>c3-c2 b6-a6 c2-d2 a6-b6 d2-e3 b6-c7 e3-f3 c7-d7 f3-g3 d7-e7 g3-h4 e7-f6 h4-h5
>>f6-f7 h5-g5 f7-e8 g5-f5 e8-e7
>
>
>Something is wrong here.
>
>It seems that your program finished depth 23 with Kb1 as the best move
>It means that the program should start searching Kb1
>at depth 24 and get a score for it.
>
>I do not understand why it did not get a score for it at depth 24 and getting a
>score for it is not related to hash tables.
>
>Uri


My guess is that the engine did get a score for the best move of the previous
iteration but doesn't write that in the logfile (it only writes information
after the completion of an iteration, or so it seems).
But only Andrew can know ...

Martin



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