Author: Bernhard Bauer
Date: 04:52:17 06/01/99
Go up one level in this thread
On June 01, 1999 at 06:32:05, Bernhard Bauer wrote:
>On June 01, 1999 at 02:18:27, Eugene Nalimov wrote:
>
>>1. Chess program searches much faster when one move is significally better than
>>all others - there are a lot of cutoffs in the tree, "fast" evaluation is
>>sufficient, null move works almost each time, etc.
>>
>>2. Crafty 16.6 sees right move in that position early because of the poor moves
>>ordering. When it started to consider the right move, it's effective search
>>depth is much higher, because to necesary information is stored in the hash
>>table. And it's stored there because program earlier evaluated (and discarded) a
>>line that resulted in the same board position.
>>
>>3. Due to the modifications made in parallel search in 16.8 (it splits tree at
>>the root, if I remember it correctly), it now considers right move *before*
>>considering the bad move that nevertheless stores necessary information in the
>>hash tables.
>>
>>4. So, till ply 26, 16.8 has no move that is much better than all other moves.
>>That is why it takes 16.8 much longer to go to some depth compared to 16.6.
>>
>>Eugene
>>
>
>Practically that means that you cannot use Crafty 16.8 with mt>1 for solving
>this type of position since Crafty 16.8 cannot find usefull data in the hash
>table and will *not* give the solution move back in reasonable time.
>
>Here I give 4 other positions of the same type. Their solution relays hevily
>on the use of hash tables.
>
>F. Sackmann, 1913 FEN: 8/8/2p/k1p1K/p1P/P/8/8 w
>M. Botwinnik, 1939 FEN: 8/1k/p/p2p2K/P2P/8/8/8 w
>C. Locock, 1892 FEN: 6k/3p/3p/3P/4P1p/6P/8/K w
>C. Locock, 1892 FEN: 6k/3p/3p/3P/4P1p/6P/8/K b
>
>Enjoy.
>Kind regards
>Bernhard
>
I'd like to add some results for the above positions for Crafty 16.6
and Crafty 16.8 running on one processor (mt=1) which show, that it's *not*
only the parallel search modification leading to worse results.
Crafty had 2 min/pos. The ply number is the number of full (completed) plies.
ply time score move
F. Sackmann 16.6 34 1:25 9.70 Kf5 good
16.8 24 1:42 2.16 Kf5 good
ply time score move
M. Botwinnik 16.6 25 2.89 1.73 Kf5 good
16.8 24 39.02 1.26 Kf5 good
ply time score move
C. Locock 16.6 32 1:25 3.95 Kb1 good
16.8 25 1:22 0.37 Kb2 bad
ply time score move
Fine 70 16.6 31 2.94 3.21 Kb1 good
16.8 28 1:58 3.13 Kb1 good
So some doubts still remain for the sequential search, at least for my
executables running on my system.
Kind regards
Bernhard
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