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Subject: Re: pawn endgame position

Author: Robert Hyatt

Date: 08:53:04 01/23/01

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On January 23, 2001 at 10:36:04, Uri Blass wrote:

>On January 23, 2001 at 10:12:24, Robert Hyatt wrote:
>
>>On January 23, 2001 at 03:06:53, Dusan Dobes wrote:
>>
>>>On January 22, 2001 at 15:57:52, Dann Corbit wrote:
>>>
>>>>>I am interested if "your" engine could resist to play 46.Qe6+ in a blitz game.
>>>>>
>>>>>[D]6k1/2pq4/5Q2/p2PPP2/1p1P4/8/P6P/7K w
>>>>>
>>>>>Best wishes,
>>>>>Steffen.
>>>>>
>>>>>[Event "ICS rated blitz match"]
>>>>
>>>>Phalanx has a time of it:
>>>>
>>>>[ white, 1 ]
>>>>6k1/2pq4/5Q2/p2PPP2/1p1P4/8/P6P/7K w
>>>>
>>>>6k1/2pq4/5Q2/p2PPP2/1p1P4/8/P6P/7K w
>>>>    -> increment adds 1440 s to soft time limit
>>>>    -> soft time limit 3154.28 s
>>>>    -> hard time limit 41599.9 s
>>>>  6    654   112   213089  Qf6-e6  Qd7-f7  Pf5-f6  Pa5-a4  Qe6-c8  Kg8-h7
>>>>                           Pe5-e6  Qf7xf6  Qc8xc7  Kh7-g6
>>>>  6 ->   0:01.60   305919   0 turns
>>>>  7    654   583  1226489  Qf6-e6  ??
>>>>  7    352   742  1585651  Qf6-e6  Qd7xe6  Pf5xe6  Pa5-a4  Pd5-d6  Pc7xd6
>>>>                           Pe5xd6  Kg8-f8  Pd6-d7  Kf8-e7  Pd7-d8B  Ke7xd8
>>>>                           Ph2-h4  Kd8-e7
>>>>  7    357   762  1623830  Qf6-g6  !
>>>>  7    525   919  1926808  Qf6-g6  Kg8-f8  Qg6-h6  Kf8-g8  Qh6-g5  Kg8-f8
>>>>                           Kh1-g1  Qd7xd5
>>>>  7 ->   0:10.26  2108193   1 turn
>>>>  8    525  1161  2360687  Qf6-g6  Kg8-f8  Qg6-h6  Kf8-g8  Qh6-g5
>>>>  8 ->   0:23.94  4694659   0 turns
>>>>  9    525  2935  5710337  Qf6-g6  Kg8-f8  Qg6-h6  Kf8-g8  Qh6-g5
>>>>  9    526  3916  7666834  Qf6-g5  Kg8-f8  Pd5-d6  Pc7xd6
>>>>  9 ->   1:10.73 13328419   1 turn
>>>> 10    526  8747 16329005  Qf6-g5  Kg8-f8  Pd5-d6  Pc7xd6  Pe5-e6  Qd7-b7
>>>>                           Kh1-g1  Qb7-g7  Qg5xg7  Kf8xg7  Pe6-e7  Kg7-f7
>>>> 10 ->   3:58.68 42938008   0 turns
>>>> 11    526 40425 71196909  Qf6-g5  Kg8-f8  Pd5-d6  Pc7xd6  Qg5-h6  Kf8-g8
>>>>                           Pe5-e6  Qd7-b7  Kh1-g1  Qb7-g7
>>>> 11 ->  17:32.80 184157117   0 turns
>>>
>>>So that's 7.62 seconds to switch to a different move.
>>>Phalanx has special knowledge that helps it to see
>>>those things quickly. It has huge extensions (like several
>>>full plies) on piece exchanges leading to pawn-only endgames.
>>>
>>>Dusan
>>
>>
>>I think you are overlooking the PV.  IE it is _still_ showing a queen exchange,
>>just not instantly.  IE at depth=10.  Trading on g7.  Doesn't matter where
>>you trade, white loses this if the b-pawn stays on the board.
>
>I think that programs have not time to extend enough in positions that are at
>distance of 10 plies from the root.
>
>Practically it can see that Qe6 is not good at the root and I guess that in a
>practical game it will also see 10 plies later the same problem.
>
>Uri


Maybe not.  IE it doesn't seem to understand that the b-pawn is going to
win the game if queens come off.  It doesn't matter whether you see it at
the root or at the tips.  You either have to search deep enough to see this
problem, or realize that there are other moves that prevent it from happening,
completely.

I'm going to file this one away as it is critical to get these right.  I have
the necessary code to detect this as won for black with no queens on, but I
don't quite do it yet for safety reasons.  But it has to be done eventually.

IE if you back those white pawns up and block them with black pawns, Crafty
will _instantly_ know to not trade queens as white, and will try to trade as
black.  But that isn't enough to offset the passed pawns white has, yet...
yet being the operative word. :)



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