Author: Gerd Isenberg
Date: 11:45:23 03/11/03
Go up one level in this thread
On March 11, 2003 at 14:13:52, Robert Hyatt wrote:
>On March 10, 2003 at 17:43:30, Gerd Isenberg wrote:
>
>>On March 10, 2003 at 17:10:43, Tom King wrote:
>>
>>>On March 10, 2003 at 17:06:10, Gerd Isenberg wrote:
>>>
>>>>On March 10, 2003 at 14:49:30, Tom King wrote:
>>>>
>>>>>Hi all,
>>>>>
>>>>>One search extension which most programs seem to use is the passed pawn pushing
>>>>>extension. When a move is made which is a passed pawn push to the 7th rank, we
>>>>>extend the search by a ply.
>>>>>
>>>>>My programs has got away without this extension for years. Or perhaps "got away"
>>>>>isn't right.. there have been losses which this extension might have prevented.
>>>>>
>>>>>Anyway, what do people think of this extension. Worth having? If so, what value
>>>>>would you attach to it?
>>>>>
>>>>>Regards (and hi to all),
>>>>>Tom
>>>>>tom@silentshark.co.uk
>>>>
>>>>Hi Tom,
>>>>
>>>>i do some fractional extensions with passers. Not only if they push or capture
>>>>foreward to the 6th or 7th rank, even if a opposite "guard" pawn in backward or
>>>>knight distance (re)captures (but no push) from it's base rank (own 7th rank) to
>>>>the "right" side, which establish an own passer on the 6th rank. I consider the
>>>>number of advanced passers per side, supporting and defending pieces. A lot of
>>>>code, specially at interiour nodes or near the root to look for further
>>>>recuductions of determined extensions.
>>>>
>>>>Even if these extensions work fine in some testpositions, i requires a lot of
>>>>effort to tune them for tournament play. Most often i do it by "gut feel".
>>>>
>>>>One thing i tried to control extensions with is to vary the amount of fractions
>>>>to become one ply. I tried to vary it by search depth and by the relative amount
>>>>of extensions so far.
>>>>
>>>>Regards,
>>>>Gerd
>>>
>>>Hi Gerd,
>>>
>>>Sounds like your passed pawn extensions are very sophisticated - doesn't this
>>>analysis slow up your search?
>>
>>Yes, but for nodes with depth left > 0. For leave nodes i use simpler and faster
>>code so i believe it pays off. The final fractional depth remainder at leave
>>nodes triggers some qsearch features, to make the qsearch width dependend on the
>>remaining fractional depth, eg. check moves or an optional quite hint move (if
>>any) from eval.
>>
>>>
>>>I'm sure you are dead right about the test positions. I gave up with testsuites
>>>a while back, and now just use hundreds of test games to determine whether a
>>>change is beneficial or not.
>>>
>>>Regards,
>>>Tom
>>
>>That's the right way to do it - but there are so many screws and switches.
>>I still use some testpositions and during tournament play i'll hope let the
>>heuristics fit ;-)
>>
>>This position was sensible to passed pawn extensions for me.
>>After IsiChess lost the game againts Shredder in Maastricht after c3? i did some
>>extension (passed pawn reductions but some other additional extensions) and even
>>eval tuning to solve this - but don't ask me whether IsiChess is stronger now.
>>
>>[D] 8/k1p1r3/p2b3p/5ppq/1np5/6P1/1R1N1P1P/R4QK1 b - - ; am c3
>>
>>
>>Regards,
>>Gerd
>
>
>This position seems to be less about passed pawns and more about king safety >and check extensions.
Yes, aggreed - but even too aggressive passed pawn extensions slowed things down
a bit.
>IE after c3, Rxb4 threatens Qxa6. Crafty says +2 here after only 4
>plies and
>zero seconds, for example. I don't think the pawn on c3 means a thing here.
Aha, that's great. IsiChess had some more problems. This was more an eval than
an extension issue. Does Crafty really see the winning line (after 43...c3)
including 49.Rxd6?
44.Rxb4 Qe2 45.Ra4 cxd2 46.Rxa6+ Kb7 47.Qb1+ Kc8 48.Qxf5 Re6 49.Rxd6
[D] 8/k1p1r3/p2b3p/5ppq/1n6/2p3P1/1R1N1P1P/R4QK1 w - -
[Event "10. WCCC 2002 Maastricht"]
[Site "?"]
[Date "2002.07.06"]
[Round "1"]
[White "Shredder"]
[Black "IsiChess X"]
[ECO "C45"]
[Result "1-0"]
1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Nf6 5. Nxc6 bxc6
6. e5 Qe7 7. Qe2 Nd5 8. c4 Ba6 9. b3 O-O-O 10. Bb2 g6
11. Qd2 Nb6 12. Bd3 d5 13. cxd5 Bxd3 14. Qxd3 Rxd5 15. Qa6+
Kb8 16. O-O Bg7 17. Na3 Qb4 18. Rad1 Ra5 19. Nc2 Qc5
20. Qd3 Rxa2 21. Rb1 Ka8 22. Rfc1 Rxb2 23. Rxb2 Bxe5
24. Ra2 Nd5 25. b4 Qb5 26. Qa3 Qb7 27. Ne1 Nxb4 28. Rb1 c5
29. Nf3 Bd6 30. Rab2 f5 31. Ng5 a6 32. Nf3 Re8 33. Qb3 Qd5
34. Qa4 Re7 35. Rd2 Qc4 36. Qd1 h6 37. Rc1 Qe6 38. Qf1 g5
39. Re1 Qf7 40. Ra1 Ka7 41. Rb2 c4 42. Nd2 Qh5 43. g3 c3
{(De2)} 44. Rxb4 Qe2 45. Rba4 cxd2 46. Rxa6+ Kb7
47. Qb1+ Kc8 48. Qxf5+ Re6 49. Rxd6 cxd6 {(De1+)}
50. Ra8+ Kd7 51. Ra7+ Kc6 52. Qc2+ Kd5 53. Ra5+ Kd4
54. Qb2+ Kc4 55. Qb5+ Kc3 56. Ra3+ Kd4 57. Ra4+ Kc3
58. Qb4+ Kc2 59. Ra2+ Kd3 60. Ra3+ Kc2 61. Rc3+ Kd1
62. Qb1# 1-0
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