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Subject: Re: Turning null-move off

Author: Robert Hyatt

Date: 07:56:38 10/08/01

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On October 08, 2001 at 07:29:04, Bernhard Bauer wrote:

>On October 07, 2001 at 21:39:52, Robert Hyatt wrote:
>
>>
>>2.  You can tone down (or even disable) the null-move search.  You can
>>try sel=2/3 (the default) then sel=2/2, sel=1/1, and finally sel=0/0 which
>>will turn null-move off.  This will further reduce the search depth and overall
>>strength.
>>
>
>From my experience sel=0/0 doesn't turn null-move completely off.
>Here an example with sel=0/0
>
>[D]4B/8/6N/5p/1r4p/6pk/7b/4K2Q w - -
>
>
>        (4)    6->   1.90  -0.44   1. Bc6 Rb1+ 2. Ke2 Rxh1 3. Nf4+ Kh4
>                                   4. Bxh1 Kg5 5. Ke3
>        (3)    7     1.96  -0.22   1. Bc6 Rb1+ 2. Ke2 Rxh1 3. Nf4+ Kh4
>                                   4. Bxh1 Bg1 5. Bg2 Bd4
>               7     2.75     ++   1. Kd2!!
>        (2)    7     3.79   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3
>        (2)    7->   6.29   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3
>               8     8.14   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3
>        (2)    8->  14.57   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3
>               9    20.50   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3 10. Nf4
>        (2)    9->  42.50   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3 10. Nf4
>              10     1:05   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3 10. Nf4 Bxf4
>        (2)   10->   2:22   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3 10. Nf4 Bxf4
>              11     3:35   0.00   1. Kd2 g2 2. Qe1 g1=Q 3. Qh4+ Kg2 4.
>                                   Bc6+ Re4 5. Bxe4+ fxe4 6. Qxg4+ Kh1
>                                   7. Qxe4+ Qg2+ 8. Ke3 Qxe4+ 9. Kxe4
>                                   Bg3 10. Nf4 Bxf4 11. Kxf4 Kh2
>             time=5:00  cpu=201%  mat=4  n=142525014  fh=89%  nps=474k
>             ext-> chk=10823921 cap=287226 pp=207595 1rep=668532 mate=112510
>             predicted=0  nodes=142525014  evals=28834988
>             endgame tablebase-> probes done=0  successful=0
>             hashing-> trans/ref=47%  pawn=99%  used=99%
>             SMP->  split=1018  stop=90  data=7/32  cpu=10:05  elap=5:00
>
>
>Kind regards
>Bernhard


I'm not sure what that is supposed to show.  But look at option.c to see how
the selective command changes null_min and null_max, then look at search.c
(the only place a null-move search is done) to see how it uses those two
values.  0/0 will definitely turn it off...

Completely...



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