Author: Robert Hyatt
Date: 19:25:24 03/18/98
Go up one level in this thread
On March 18, 1998 at 15:12:07, Christophe Theron wrote:
>On March 18, 1998 at 06:31:37, Ernst A. Heinz wrote:
>
>>On March 17, 1998 at 21:42:52, David Blackman wrote:
>>
>>>Actually about positions like KNkp and how thay should be evaluated.
>>>
>>>It looks like Junior, Crafty and maybe others are evaluating such
>>>positions
>>>as not winnable as soon as they appear in the tree. Surely it would be
>>>better
>>>to allow the tree to grow out to its normal depth, and just detect these
>>>(probably drawn) positions in the normal end-node evaluator. That way
>>>your program "knows" it is a draw, unless the win is shallow enough to
>>>see in the search, in which case it finds it.
>>>
>>>Of course that makes the search tree a bit bigger for a given depth.
>>>Has anyone tried both approaches to see how big the cost is?
>>
>>"DarkThought" uses fast rules of thumb to disable the draw detection
>>heuristic in such cases where it might fail. The costs are negligible --
>>both as for runtime overhead and size of search tree.
>>
>>"DarkThought" solves all the critical positions posted in this thread.
>>
>>W.r.t. Christophe Theron's analysis of the Nolot-Position with key move
>>Ng4 I like to add that for "DarkThought" the depth where it finds the
>>solution not only depends on the null move search but also quite
>>strongly
>>on the aggressiveness of pawn-related extensions.
>>
>>=Ernst=
>
>You are right. My point was to show that null move or related techniques
>had a significant impact on this position.
>
>Unfortunately, others parameters biased the result. So here is another
>position given by Chrilly Donninger in his famous paper from ICCA
>Journal, Sep 93:
>
>White:
>Pawn b4
>Rook d4
>King f2
>
>Black:
>Pawn a6 b5 h2
>Rook g6
>King h1
>
>White to move. The key is 1.Rd1+, which is mate in 7. After 1...Rg1,
>black is in zugzwang. White plays for example 2.Rf1, and wins.
>
>Genius3/5 finds the key in 0.5 second or so at "ply" 5, which means IMO
>ply 8 or 9 (K5-100, 384Kb hash).
>
>Rebel9 finds that 1.Rd1+ has a positive score at ply 9 in 1 second, but
>score is only +4.80, and finds the mate at ply 10 in 2 seconds (K5-100,
>10Mb hash).
>
>ChessMaster 4000 finds that 1.Rd1+ has a positive score at ply 7 in 2
>seconds (+1.23), and finds the mate at ply 8 in 3 seconds.
>
>Fritz2 didn't find the solution in 10 minutes.
>
>I would like to hear about results of others programs in this position.
>I suspect that check and pawns extensions would have an impact on the
>time needed to find the mate, but my only point is: does program X finds
>the mate?
>
>
> Christophe
here's crafty running on my notebook, default (small) hash and all:
depth time score variation (1)
1 0.01 -4.98 1. Ke3
1-> 0.01 -4.98 1. Ke3
2 0.02 -5.14 1. Ke3 Re6+ 2. Kf4
2 0.03 -5.09 1. Rf4 Re6
2-> 0.03 -5.09 1. Rf4 Re6
3 0.04 -4.95 1. Rf4 Re6 2. Kg3
3-> 0.05 -4.95 1. Rf4 Re6 2. Kg3
4 0.06 -- 1. Rf4
4 0.06 -5.37 1. Rf4 Rg2+ 2. Kf1 Rd2 3. Rf2 Rxf2+
4. Kxf2
4 0.08 ++ 1. Rd1+!!
4 0.08 -5.06 1. Rd1+ Rg1 2. Rd8 Rg2+ 3. Ke3 Kg1
4-> 0.08 -5.06 1. Rd1+ Rg1 2. Rd8 Rg2+ 3. Ke3 Kg1
5 0.10 ++ 1. Rd1+!!
5 0.11 -4.48 1. Rd1+ Rg1 2. Rd6 Ra1 3. Rg6 Ra3 4.
Rg8
5-> 0.12 -4.48 1. Rd1+ Rg1 2. Rd6 Ra1 3. Rg6 Ra3 4.
Rg8
6 0.14 -4.64 1. Rd1+ Rg1 2. Rd6 Ra1 3. Rg6 a5 4.
bxa5 Rxa5 5. Ke3
6-> 0.15 -4.64 1. Rd1+ Rg1 2. Rd6 Ra1 3. Rg6 a5 4.
bxa5 Rxa5 5. Ke3
7 0.22 -4.61 1. Rd1+ Rg1 2. Rd6 Ra1 3. Re6 Ra2+
4. Kf3 Ra3+ 5. Ke4 Ra2
7-> 0.23 -4.61 1. Rd1+ Rg1 2. Rd6 Ra1 3. Re6 Ra2+
4. Kf3 Ra3+ 5. Ke4 Ra2
8 0.30 -4.48 1. Rd1+ Rg1 2. Rd6 Ra1 3. Re6 Ra2+
4. Kf3 Ra3+ 5. Ke4 Ra1 6. Rf6
8-> 0.43 -4.48 1. Rd1+ Rg1 2. Rd6 Ra1 3. Re6 Ra2+
4. Kf3 Ra3+ 5. Ke4 Ra1 6. Rf6
9 0.66 ++ 1. Rd1+!!
9 0.68 Mat07 1. Rd1+ Rg1 2. Rf1 a5 3. bxa5 b4 4.
a6 Rxf1+ 5. Kxf1 b3 6. a7 b2 7.
a8=Q#
9-> 0.73 Mat07 1. Rd1+ Rg1 2. Rf1 a5 3. bxa5 b4 4.
a6 Rxf1+ 5. Kxf1 b3 6. a7 b2 7.
a8=Q#
time: 0.74 cpu:83% mat:-2 n:51447 nps:10000
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.