Author: William Bryant
Date: 15:47:49 09/10/99
Go up one level in this thread
On September 10, 1999 at 00:19:37, Robert Hyatt wrote:
>Here is an interesting position given to me by Steffen Jakob:
>
> /p/P5p/7p/7P/4kpK/// w
>
I tried this on Screamer (G3 266) and got the PV below.
Welcome to Screamer (Beta) 1.00 Build 36
Current Hash Table Size: 8192 K bytes
Debug Control On
PVS Search
NULL move Search
New Game ...
Move 1 W>>
The Current Search Time: 300 seconds
New Board Position
8/p7/P5p1/7p/7P/4kpK1/8/8 w - - 0 0
Move 1 W>>
PLY NODES TIME SCORE PV
____________________________________________
5 665 0:00 -10.95 Kh2 f2 Kg2 Ke2 Kh3 f1=Q+ Kg3
6 1185 0:00 -10.95 Kh2 f2 Kg2 Ke2 Kh3 f1=Q+ Kg3
7 1904 0:00 -10.95 Kh2 f2 Kg2 Ke2 Kh2 f1=Q Kg3
8 4177 0:00 -12.39 Kh2 f2 Kg2 Ke2 Kh2 Kf3 Kh3 f1=Q+ Kh2 Qxa6
9 9010 0:00 -13.27 Kh2 f2 Kg2 Ke2 Kh3 f1=Q+ Kh2 Qf4+ Kh3 Qg4+ Kh2
Qxh4+ Kg2
10 22310 0:00 -13.57 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 Qf4+
11 107384 0:01 -13.57 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 Qf4+
12 359601 0:04 -99.88 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5 Kf3 g6 Qg2+
13 988159 0:11 -99.88 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5 Kf3 g6 Qg2+
14 2764683 0:31 -99.88 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5 Kf3 g6 Qg2++
15 7232763 1:21 -99.88 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5 Kf3 g6 Qg2++
----- Search Stopped -----
15 8745125 1:30 -99.88 Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5 Kf3 g6 Qg2++
Total Search Time: 1:30
Move: Kh2
I don't find mates shorter than 6 moves (12 plies).
If I understand you solution correctly, if you fail high (regular search or
null move search) with a score that is creater than the Mate score limit,
you adjust that score to the mate score limit for fail high stores in the
hashtable. Also, don't store a best move in this case.
ie in sort-of-pseudocode
if (Score>alpha) {
if (Score>beta) {
long StoreScore = (Score>MateScoreLimit)?MateScoreLimit:Score;
HashStore(CurHashSig, NoMove, StoreScore, LOWER):
}
}
William
wbryant@ix.netcom.com
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