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Subject: Re: curious Rybka behaviour

Author: M Hurd

Date: 15:41:54 01/27/06

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On January 27, 2006 at 13:01:33, Bernardo Wesler wrote:

>I noticed that Rybka improves its performance against F9,Sh9 and TogaII if it
>plays with low hash tables sizes; for example having 1gb as a total ram, Rybka
>plays better with 32 mb hash than with 128, 256 or 512......
>Have anybody else noticed this?
>If so, why?
>Thx

Hello Bernado

Have a look at the following position :

[D]r3r1k1/1bq2np1/1p1ppp1p/7B/nPP1PP1N/6P1/4Q2P/B1R1R1K1 w - - 0 34

Analysis with Rybka using 32 mb hash time to find Bxf6 = 2o mins 54 secs
Analysis with Rybka using 256 mb hash time to find Bxf6 = 9 mins 53 secs

New game - Rybka 1.01 Beta 13 32-bit
r3r1k1/1bq2np1/1p1ppp1p/7B/nPP1PP1N/6P1/4Q2P/B1R1R1K1 w - - 0 1

Analysis by Rybka 1.01 Beta 13 US 32-bit: 32 mb Hash

1.Bd4
  =  (-0.05)   Depth: 3   00:00:00
1.Qg4
  ²  (0.36)   Depth: 3   00:00:00
1.Qg4
  ²  (0.45)   Depth: 4   00:00:00
1.Qg4 Qe7
  ²  (0.47)   Depth: 5   00:00:00
1.Qg4 Qe7 2.Bd4
  ²  (0.47)   Depth: 6   00:00:00  11kN
1.Qg4 Qe7 2.Bd4 Ra7
  ²  (0.49)   Depth: 7   00:00:00  29kN
1.Qg4 Qe7 2.Bd4 Ra7 3.Ra1
  ²  (0.54)   Depth: 8   00:00:01  83kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Rc2 Ra7
  ²  (0.53)   Depth: 9   00:00:04  214kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Ra1 b5 4.Ng6
  ²  (0.59)   Depth: 10   00:00:08  398kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Ra1 b5 4.Ng6 Qd8
  ²  (0.63)   Depth: 11   00:00:20  998kN
1.Qg4 Qe7 2.Bd4 Rac8 3.f5 e5 4.Be3
  ²  (0.58)   Depth: 12   00:00:33  1642kN
1.Qg4 Qe7 2.Bd4 Rac8 3.Qd1 Qd7 4.Rc2 b5 5.Qg4 Qe7 6.Qd1 Qd7 7.Qg4 Qe7
  ²  (0.59)   Depth: 13   00:01:01  3022kN
1.Qg4 Qe7 2.Rc2 Bc6 3.Bd4 Bd7 4.f5 e5 5.Be3 Rec8 6.Ra1
  ²  (0.69)   Depth: 14   00:02:42  7712kN
1.Qg4 Qe7 2.Rc2 Rac8 3.Ra2 Ra8 4.Bd4
  ±  (0.72)   Depth: 15   00:06:28  18045kN
1.Qg4 Qe7 2.Rc2 Bc6 3.Rd2 Bb7 4.Ng6 Qd8 5.e5 f5
  ±  (0.93)   Depth: 16   00:18:19  50018kN
1.Bxf6 gxf6 2.Qg4+ Kh8 3.Qg6 Re7 4.Qxf6+ Kg8 5.Qg6+
  ±  (1.10)   Depth: 16   00:20:54  56938kN

New game - Rybka 1.01 Beta 13 32-bit, Blitz:10' Swadlincote
r3r1k1/1bq2np1/1p1ppp1p/7B/nPP1PP1N/6P1/4Q2P/B1R1R1K1 w - - 0 1

Analysis by Rybka 1.01 Beta 13 US 32-bit: 256 mb hash

1.Bd4
  =  (-0.05)   Depth: 3   00:00:00
1.Qg4
  ²  (0.36)   Depth: 3   00:00:00
1.Qg4
  ²  (0.45)   Depth: 4   00:00:00
1.Qg4 Qe7
  ²  (0.47)   Depth: 5   00:00:00
1.Qg4 Qe7 2.Bd4
  ²  (0.47)   Depth: 6   00:00:00  11kN
1.Qg4 Qe7 2.Bd4 Ra7
  ²  (0.49)   Depth: 7   00:00:00  29kN
1.Qg4 Qe7 2.Bd4 Ra7 3.Ra1
  ²  (0.54)   Depth: 8   00:00:01  83kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Rc2 Ra7
  ²  (0.53)   Depth: 9   00:00:04  214kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Ra1 b5 4.Ng6
  ²  (0.59)   Depth: 10   00:00:08  398kN
1.Qg4 Qe7 2.Bd4 Bc6 3.Ra1 b5 4.Ng6 Qd8
  ²  (0.63)   Depth: 11   00:00:21  995kN
1.Qg4 Qe7 2.Bd4 Rac8 3.f5 e5 4.Be3
  ²  (0.58)   Depth: 12   00:00:33  1622kN
1.Qg4 Qe7 2.Rc2 Rac8 3.Ra2
  ²  (0.64)   Depth: 13   00:01:19  3917kN
1.Qg4 Qe7 2.Rc2 Rac8 3.Ra2 Ra8 4.Bd4 Bc6 5.Rea1 b5 6.Ng6
  ±  (0.77)   Depth: 14   00:03:01  8855kN
1.Qg4 Qe7 2.Rc2 Rac8 3.Ra2 Ra8 4.Bd4 Bc6 5.Rea1 b5 6.Ng6 Qd8
  ±  (0.72)   Depth: 15   00:04:18  12373kN
1.Qg4 Qe7 2.Rc2 Rac8 3.Ra2 Ra8 4.Bd4 Bc8 5.f5 e5 6.Be3 Bd7 7.Rc1
  ²  (0.69)   Depth: 16   00:07:46  21488kN
1.Bxf6 gxf6 2.Qg4+ Kh8 3.Qg6 Re7 4.Qxf6+ Kg8 5.Bg4 Bc8 6.Qg6+ Kh8 7.f5 Ne5
  ±  (1.10)   Depth: 16   00:09:53  27020kN

Depth 14 and below is quicker with 32 mb hash whereas Depth 15 and above is
quicker with 256 mb hash on my machine with this articular position.

I do not have enough ram to try 512 mb but would guess that would find Bxf6
quicker again.

So if you play fast games a lower hash size will be more suitable wheras for
long games bigger is better if you have enough ram to spare.

Hope this helps.

Regards

Mike



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