Author: Robert Hyatt
Date: 13:10:56 09/06/02
Go up one level in this thread
On September 06, 2002 at 05:17:01, David Dory wrote:
>On September 05, 2002 at 21:46:41, scott farrell wrote:
>
>>Hi guys,
>>
>>I hope someone can give me some ideas, or can understand this pattern.
>>
>>this is the fen position
>>
>>[D]7k/pp3p1p/1np5/5N2/1P2P1NR/7P/3r2PK/2r5 b - - 0 50
>>
>>clearly the best move is Nd7 (aka B6D7)
>>Rcc2 (aka c1c2) is not too bad either
>>The rest pretty much lead to mate.
>>My program works that out pretty quickly, but changes its mind during depth 10
>>to D2C2.
>>When searching depth 11 - its sees that D2C2 leads straight to being mated (in 2
>>plies - mate in 1 - I think). The move ordering obviously gets screwed up, and
>>it does an almost reverse alpha-beta search.
>>I assume this is a bug somewhere in my search, does anyone have any ideas?
>>
>>this is my programs analysis:
>>
>>d6/8(3) 4.28 0.38secs 6820 C1C2 G4E3 C2A2 H4G4 B6D7 G4G7
>>->6/10(3) 4.28 0.71secs 38971 C1C2 G4E3 C2A2 H4G4 B6D7 G4G7
>>d7/12(3) 4.59 0.88secs 55850 C1C2 F5E3 C2B2 G4F6 H8G7 F6H7 B2B4
>>d7/12(4) 4.85 1.7secs 137123 B6D7 F5H6 F7F6 G4E3 H8G7 H6F5
>>->7/12(4) 4.85 1.7secs 137141 B6D7 F5H6 F7F6 G4E3 H8G7 H6F5
>>d8/12(3) 4.22 1.98secs 162918 B6D7 F5H6 F7F6 H4H5 C1C2 H6F7
>>->8/14(4) 4.22 4.01secs 364580 B6D7 F5H6 F7F6 H4H5 C1C2 H6F7
>>d9/16(4) 4.69 6.87secs 654405 B6D7 H4H6 C1C2 G4E3 C2B2 H6D6 D2D6
>>->9/16(4) 4.69 7.36secs 711939 B6D7 H4H6 C1C2 G4E3 C2B2 H6D6 D2D6
>>d10/18(4) 3.86 12.3secs 1292913 B6D7 H4H6 C6C5 B4B5 C1E1 F5D6 E1F1 D6C4 D2C2
>>H6D6
>>d10/18(4) 3.9 19.17secs 1941731 D2C2 H2G3 C6C5 B4C5
>>->10/24(4) 3.9 30.43secs 3164993 D2C2
>>d11/19(2) -501.99 30.59secs 3178776 PV miss at root:D2C2
>>d11/20(3) -1.03 41.52secs 4470207 D2G2 H2G2 C1C2 G2F3 C2C3 F3E2 B6D7 F5D6
>>H8G7 D6B7 C3G3 G4F2 G7F6
>>d11/20(3) 3.89 43.01secs 4611313 C1C2 F5E3 C2B2 G4F6 H8G7 E4E5 G7F8 F6H7
>>d11/22(4) 4.59 116.28secs 11658630 B6D7 G4E3 D7E5
>>
>>This is from crafty:
>>
>>({10:Mat06} 35. ... Ra2 36. Nf6 Rxg2+ 37. Kxg2 Rc2+ 38. Kg3 Rc3+ 39. Kg4 Rxh3
>>40. Rxh3 Nc4 41. Rxh7# +-)
>>(yes beleive it or not, my engine played Ra2 - a few months back without
>>extensions)
>>({10:-5.14} 35. ... Nd7 36. Rh6 Rb1 37. Rd6 Rxd6 38. Nxd6 Kg7 39. Nxb7 h5 40.
>>Ne3 Rxb4 -+)
>>({10:-1.74} 35. ... Rcc2 36. Nf6 Rxg2+ 37. Kh1 Rh2+ 38. Kg1 Rcg2+ 39. Kf1 Rg7
>>40. Nxg7 Kxg7 41. Ne8+ Kg8 42. Nd6 Rb2 43. Rf4 Rb1+ 44. Kg2 Rb2+ 45. Kf3 -+)
>>({10:+2.46} 35. ... Nd5 36. exd5 Rcc2 37. Nge3 Rb2 38. Re4 h5 39. dxc6 bxc6 40.
>>Ng3 c5 41. bxc5 +-)
>>
>>
>>normal moves:
>>C1H1,C1G1,C1F1,C1E1,C1D1,C1B1,C1A1,C1C2,C1C3,C1C4,C1C5,D2D1,D2G2,D2F2,D2E2,D2C2,
>>D2B2,D2A2,D2D3,D2D4,D2D5,D2D6,D2D7,D2D8,C6C5,B6C4,B6A4,B6D5,B6D7,B6C8,B6A8,H7H5,
>>H7H6,F7F6,A7A5,A7A6,H8G7,H8G8,
>>OUT OF CHECK moves:
>>C1H1,C1G1,C1F1,C1E1,C1D1,C1B1,C1A1,C1C2,C1C3,C1C4,C1C5,D2D1,D2G2,D2F2,D2E2,D2C2,
>>D2B2,D2A2,D2D3,D2D4,D2D5,D2D6,D2D7,D2D8,C6C5,B6C4,B6A4,B6D5,B6D7,B6C8,B6A8,H7H5,
>>H7H6,F7F6,A7A5,A7A6,H8G7,H8G8,
>>qsearch moves:
>>D2G2,
>>sideotmove token:
>>7k/pp3p1p/1np5/5N2/1P2P1NR/7P/3r2PK/2r5/ b - - 0 50
>>searchProbeThread starting
>>start search from 6 to 30
>>
>>Scott
I don't see this as a "pattern" problem. It looks like you need to check
two things:
(1) your search extensions. IE are you extending on checks at least? and
a whole ply?
(2) are you sure your checkmate detection is working? Allowing a short mate
with a 10 ply search suggests you are overlooking something. The question is,
what? and why?
Are you doing any odd stuff like futility pruning, razoring, null-move, etc?
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