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Subject: Re: Chess program improvement project (copy at Winboard::Programming)

Author: Tord Romstad

Date: 15:05:24 03/07/06

Go up one level in this thread


On March 07, 2006 at 16:01:57, Dann Corbit wrote:

>Fruit uses late move reductions, and yet the search is perfectly symmetrical.

No, it is not.  See the following output from Fruit 2.1:

First I ask the program (freshly started, with default settings) to analyse
the initial position to depth 5:

position startpos
go depth 5
info depth 1
info depth 1 seldepth 1 score cp 26 time 0 nodes 2 pv b1a3
info depth 1 seldepth 1 score cp 54 time 0 nodes 3 pv b1c3
info depth 1 seldepth 1 time 1 nodes 21 nps 0
info depth 2
info depth 2 seldepth 2 score cp 0 time 1 nodes 44 pv b1c3 b8c6
info depth 2 seldepth 2 time 1 nodes 82 nps 0
info depth 3
info depth 3 seldepth 3 score cp 54 time 1 nodes 148 pv b1c3 b8c6 g1f3
info depth 3 seldepth 3 time 1 nodes 186 nps 0
info depth 4
info depth 4 seldepth 6 score cp 0 time 1 nodes 300 pv b1c3 b8c6 g1f3 g8f6
info depth 4 seldepth 6 time 2 nodes 976 nps 0
info depth 5
info depth 5 seldepth 9 score cp 48 time 4 nodes 1729 pv b1c3 b8c6 g1f3 g8f6
d2d4

After a restart of the program, I try the same position with black to move:

position fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR b KQkq - 0 1
go depth 5
info depth 1
info depth 1 seldepth 1 score cp 4 time 0 nodes 2 pv a7a5
info depth 1 seldepth 1 score cp 10 time 0 nodes 4 pv b7b5
info depth 1 seldepth 1 score cp 52 time 1 nodes 8 pv d7d5
info depth 1 seldepth 1 score cp 54 time 1 nodes 19 pv b8c6
info depth 1 seldepth 1 time 1 nodes 21 nps 0
info depth 2
info depth 2 seldepth 2 score cp 0 time 1 nodes 44 pv b8c6 b1c3
info depth 2 seldepth 2 time 1 nodes 82 nps 0
info depth 3
info depth 3 seldepth 3 score cp 54 time 1 nodes 148 pv b8c6 b1c3 g8f6
info depth 3 seldepth 3 time 1 nodes 186 nps 0
info depth 4
info depth 4 seldepth 6 score cp 0 time 1 nodes 300 pv b8c6 b1c3 g8f6 g1f3
info depth 4 seldepth 6 time 3 nodes 979 nps 0
info depth 5
info depth 5 seldepth 10 score cp 48 time 4 nodes 1743 pv b8c6 b1c3 g8f6 g1f3
d7d5

As you can see, the search isn't entirely symmetrical.  The node counters and
the selective search depths differ.  If you repeat the experiment with Fruit
2.2,
you will see the same thing.

Tord



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