Author: Andrew Williams
Date: 13:47:19 05/29/01
Go up one level in this thread
On May 29, 2001 at 16:26:38, Peter Fendrich wrote:
>On May 29, 2001 at 15:42:45, Andrew Williams wrote:
>
>>On May 29, 2001 at 15:04:54, Peter Fendrich wrote:
>>
>>>On May 29, 2001 at 14:42:43, Miguel A. Ballicora wrote:
>>>
>>>>On May 29, 2001 at 14:21:13, Peter Fendrich wrote:
>>>>
>>>>>This position appeared in an ICC game: Guitje - TerraPi
>>>>>
>>>>>[D]2r3kb/5q1p/4pPp1/1p1pP3/p2P2Q1/PrP5/1P3R1R/2B3K1 w - - 0 42
>>>>>
>>>>>the last move from Terra was 41... b5
>>>>>Some moves earlier when white made g6, Terra decided to move the bishop from g7
>>>>>to h8.
>>>>>Both Rb3 and Bh8 are locked in and Terra is absolutely unaware of the
>>>>>hopeless situation. Yes, Terra lost...
>>>>>
>>>>>I see two different but connected problems for computer programs here:
>>>>> - the closed position itself
>>>>> - the two blocked pieces.
>>>>>
>>>>>How do you solve/avoid positions like this? Terra has about equal eval for this
>>>>>position.
>>>>>It is of course possible to punish pawn chains like this in order to avoid
>>>>>closed positions but is that really a solution and how to deal with blocked
>>>>>positions?
>>>>>
>>>>>//Peter
>>>>
>>>>Mobility helps a little in this respect. My program Gaviota has an small
>>>>evaluation where the mobility component is a big % of it. I gives in this
>>>>position +1.75 for white.
>>>
>>>I try to minimise the mobility factor and find other terms in order to achieve
>>>about the same effect. In many positions a heavy weight on mobility will give
>>>strange play for Terra. But herre it would help.
>>>One problem here is the K-positions. Terra gives a lot of punishment for the
>>>white K position that doesn't have any pawn shelter. In an open position that
>>>would be ok but here it is not.
>>>//Peter
>>
>>You're right. This is a nasty position.
>>
>>PM scores it statically as +0.21 for Black, which is obviously not helpful.
>>It has the same problem as Terra, insofar as it thinks that White's King is in
>>more danger than Black's. Part of the problem is that it's difficult for PM's
>>dynamic king safety factors to kick in. All it can see is that White's King
>>has less pawn shelter than Black's. How many plies from this position does it
>>take for Terra to see that Black is in serious trouble? Mine sees White at
>>+1.5 at depth nine, but that takes 2 seconds even on my Athlon 1200.
>>
>>Andrew
>
>Terra needs depth=11 to really find that. Between 9 and 11 he is slowly changing
>his mind. On my PII 300 MHz it takes more than 2 minutes to get it:
>Depth Time Eval Nodes
>----- ---- ----- -------
>11 2:24 248 8730379 Rxh7 Kxh7 Rh2 Kg8 Qh3 Bxf6 exf6 Kf8 Qh8 Qg8 f7
> Kxf7 Rh7 Qxh7 Qxh7 Kf6
>//Peter
This is my program's output:
8= 62 1 124113 1. Rh6 Rc7 2. Rfh2 Qe8 3. Bf4
9> 62 1 144075 1. Rh6 Rc7 2. Rfh2 Qe8 3. Bf4 Rf7 4. Qh3
9= 156 3 435349 1. Rh6 Rc7 2. Rfh2 Qe8 3. Qh3 Qf7 4. Rxg6 Qxg6
5. Rg2 Qxg2 6. Kxg2
10> 156 3 488379 1. Rh6 Rc7 2. Rfh2 Qe8 3. Qh3 Qf7 4. Rxg6 Qxg6
5. Rg2 Qxg2 6. Qxg2 Kf8 7. Bf4
10b 165 6 855439 1. Rh3 Rc7 2. Rfh2 Qe8 3. Qg5 b4 4. axb4
10= 169 6 875504 1. Rh3 Rc7 2. Rfh2 Qe8 3. Qg5 b4 4. axb4
11> 169 8 1137228 1. Rh3 Rc7 2. Rfh2 Qe8 3. Qg5 b4 4. axb4
11b 224 12 1771335 1. Rxh7 Kxh7 2. Rh2 Kg8 3. Qh3 Bxf6 4. exf6
11= 285 18 2828059 1. Rxh7 Kxh7 2. Rh2 Kg8 3. Qh3 Bxf6 4. exf6 Kf8
5. Qh8 Qg8 6. f7 Kxf7 7. Rh7 Qxh7 8. Qxh7 Kf6
12> 285 18 2905936 1. Rxh7 Kxh7 2. Rh2 Kg8 3. Qh3 Bxf6 4. exf6 Kf8
5. Qh8 Qg8 6. f7 Kxf7 7. Rh7 Qxh7 8. Qxh7 Kf6
12= 295 23 3794754 1. Rxh7 Kxh7 2. Rh2 Kg8 3. Qh3 Bxf6 4. exf6 Kf8
5. Qh8 Qg8 6. f7 Kxf7 7. Rh7 Qxh7 8. Qxh7 Kf6 9. Kf2
PM also takes until depth 11 to see this one.
Andrew
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