Author: Robert Hyatt
Date: 07:08:57 01/05/03
Go up one level in this thread
On January 05, 2003 at 09:59:30, scott farrell wrote:
>On January 04, 2003 at 21:52:32, Robert Hyatt wrote:
>
>>On January 04, 2003 at 21:41:31, scott farrell wrote:
>>
>>>On January 04, 2003 at 15:01:34, Robert Hyatt wrote:
>>>
>>>Yes it is about the knight on a8. A human doesnt need a horizon to see the
>>>knight on a8 should be scored way down, and will probably be lost, but most
>>>programs if it cant see it being lost inthe qsearch, consider the piece to be
>>>safe.
>>
>>Maybe. Crafty has code to hate a knight on a8, and the PV it had showed the
>>knight getting back out quickly. Here is the PV:
>
>is it specific to a8 (I am guessing that means all corners).
all corners, in fact... "a knight on the rim is dim, a knight in the corner
is dead."
>
>My code is generic, and anywhere on the board.
>
>I think it is pretty fast, I compare night moves against all pawns, and against
>enemy pawns moves, and if it is 2 or less, I iterate through those squares and
>do some static eval, like defence/attackers. It isnt too slow, as the loop is
>behind the first condition which is one some bitboard comparison, its only slow
>when a knight/bishop/rook is nearly trapped, but I think quicker than trying to
>search it out, and start failing low at successive plies.
>
>>
>> 15 1:44 0.96 2. Nxb6 Nxd3 3. Nxa8 Nf4 4. Rfe1 Nf6
>> 5. Re5 b6 6. Nc7+ Kd7 7. Na6 Bd6 8.
>> Re3 N4xh5 9. Rae1 Nxg3 10. fxg3
>>
>>As you see, in that variation, the knight gets out pretty quickly. The
>>only issue is does white have time to do that, or does white have to handle
>>some other threat by black that prevents getting the knight out? That is not
>>easy to compute for me (as a human) or crafty (as a computer).
>>
>>My gut reaction is that this is winning for _white_... not black... if white
>>plays well. If white doesn't realize that the knight is dangerously close to
>>being lost on a8 and take immediate action to extricate it, I could easily see
>>a program losing that knight by a misstep here or there...
>>
>>
>>>
>>>Thanks to bit boards, I check the mobility of knights/bishops/rooks - and I
>>>think it paid off big time here.
>>>
>>>The knight gets royally stuck on a8, and my chompster scores a knight with no
>>>move, other than into pawns and pawns attacks, as less than a pawn, and a knight
>>>with only 1 move as about half a knight.
>>>
>>>The knight on a8 has one move, but it too is trapped, and only leads back to a8.
>>
>>Maybe or maybe not. See my PV above which gets out thru c7 (with check) and
>>a6.
>>>
>>>Dorky's score moved down very rapidly with each move in the game, but didnt
>>>really take the toll of the knight into account until actually capturing it was
>>>within its horizon of 13-14 ply. Then it played all sorts of strange moves to
>>>try to prevent it, as it didnt understand that it was undefendable because it
>>>couldnt move.
>>>
>>>
>>>>On January 04, 2003 at 14:39:40, scott farrell wrote:
>>>>
>>>>>This position occured in a game chompster vs dorky on ICC (45 10 time control
>>>>>practices for CCT5).
>>>>>
>>>>>[D]r3kb1r/pp1n1pp1/1qp1p2p/3n3P/2NP1B2/3Q2N1/PPP2PP1/R4RK1 b kq - 0 14
>>>>>
>>>>>My engine says NxB is slightly winning for black, it failed high big time at
>>>>>only depth 8 !!!
>>>>>sfarrellc(C) whispers: , D10/11(11): 0.29 : D5F4 , 25.176/48.0 secs
>>>>>
>>>>>Crafty says it is +3 winning for white.
>>>>>Dorky(C) whispers: score=+2.61 depth=13 Knps=111 cpu=99% time=87.05s
>>>>>
>>>>>Here is crafty's annotation:
>>>>>({9:+2.92} 14. ... Nxf4 15. Nxb6 Nxd3 16. Nxa8 Nxb2 17. Rab1 Ba3 18. Nc7+ Kd8
>>>>>19. Na8 +-)
>>>>>({9:+1.04} 14. ... Qd8 15. Bd2 N7b6 16. Ne5 Bd6 17. Rfe1 Qh4 18. Qe4 Qxe4 19.
>>>>>Rxe4 Bxe5 20. Rxe5 +/-)
>>>>>({9:+1.52} 14. ... Qb5 15. Bd6 Nb4 16. Qe2 Nb6 17. Bxf8 Kxf8 18. b3 Nxc4 19.
>>>>>bxc4 Qg5 +-)
>>>>>({9:+1.66} 14. ... Qa6 15. Nd6+ Bxd6 16. Qxa6 bxa6 17. Bxd6 N7f6 18. Rfe1 Rd8
>>>>>19. Bc5 Nf4 +-)
>>>>>({9:+2.03} 14. ... Qb4 15. Bd2 Qa4 16. Ne4 Qa6 17. Ncd6+ Bxd6 18. Nxd6+ Ke7 19.
>>>>>Nc4 Qb5 +-)
>>>>>
>>>>>
>>>>>NxB is a clear winner !!!! It was an easy win from there.
>>>>>
>>>>>How many other engines see this? It took 19 more moves to actually recover the
>>>>>material that my engine could see coming !!!!
>>>>
>>>>
>>>>
>>>>
>>>> Crafty thinks Qd8 and Nxf4 are different in score, but not +3. If I
>>>>let crafty think, it thinks black is better with a score of -.9 after Qd8.
>>>>If I play Nxf4, it thinks white is better with a score of +1.16 and would play
>>>>Nxb6 thru depth 14, which only takes 10 seconds or so to reach.
>>>>
>>>>I haven't looked at it, but I am not sure that Nxf4 "is a clear winner"
>>>>If this is about the white knight getting stuck at a8, it _might_ be a
>>>>problem, but I doubt that any program will see it from the starting position.
>>>>
>>>>I can't get the score you posted above so I don't know what is going on there.
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