🚀 go-pugleaf

I noticed when running some of the Bratco-Kopec tests that
GNUCHESS shows some strange behaviour.

The idea is to turn off the hashtable and let it play a move:

e.g.


/usr/local/bin/gnuchessr 0 0
 
 
White 0:00  Black 0:00
 
 R N B Q K B N R
 P P P P P P P P
 - - - - - - - -
 - - - - - - - -
 - - - - - - - -
 - - - - - - - -
 p p p p p p p p
 r n b q k b n r
 
Book used 36679 of 45000 entries.
Playing without hashfile
 
Your move is? get
Enter file name: 
bk007
 
 
White 0:00  Black 0:00
 
 - N K - R - R -
 P P - - N - P P
 - - - - P - - -
 Q - - P p P - n
 B - P p - p - -
 b - p - - r - -
 - - p - b - p p
 r - - q - - k -
 
 
Your move is? hash
 
Your move is? post
 
Your move is? go
 
Move# 1    Target= 0    Clock: 0
 2.    -22    0     4331   a3b4  a5a6  b4d6  a4c2 
 3&    -49    0     5507   a3b4  a5a6  b4d6  b8c6 
 3.    -49    0     8042   a3b4  a5a6  b4d6  b8c6 
 4&    -32    1    13884   a3b4  a5a6  b4d6  b8c6  a1b1 
 4.    -32    5    88627   a3b4  a5a6  b4d6  b8c6  a1b1 
 5&    -46    7   116469   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
 5.    -46   18   284502   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
 6.    -46   20   302508   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
1. ... a3b4
Gen 725397 Node 302508 Tree 376 Eval 27031 Rate 15125 EC 16003/9238 RS hi 0 lo 0 
Hin/Hout/Tcol/Coll/Fin/Fout = 0/0/0/0/0/0
My move is: a3b4
 
Your move is? undo
 
White 0:00  Black 0:00
 
 - N K - R - R -
 P P - - N - P P
 - - - - P - - -
 Q - - P p P - n
 B - P p - p - -
 b - p - - r - -
 - - p - b - p p
 r - - q - - k -
 
 
Your move is? go
 
Move# 1    Target= 0    Clock: 0
 2.    -22    0     4437   a3b4  a5a6  b4d6  a4c2 
 3&    -49    0     5615   a3b4  a5a6  b4d6  b8c6 
 3.    -49    0     8161   a3b4  a5a6  b4d6  b8c6 
 4&    -32    1    14156   a3b4  a5a6  b4d6  b8c6  a1b1 
 4.    -32    6    89089   a3b4  a5a6  b4d6  b8c6  a1b1 
 5&    -46    8   118117   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
 5.    -46   22   286237   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
 6.    -46   24   307246   a3b4  a5a6  b4d6  b8d7  a1b1  a4c6 
2. ... a3b4
Gen 735613 Node 307246 Tree 376 Eval 32089 Rate 12801 EC 24917/30664 RS hi 0 lo 0 
Hin/Hout/Tcol/Coll/Fin/Fout = 0/0/0/0/0/0
My move is: a3b4
 
Your move is? 

=====================================
Note that at the first move computation ply 2 shows a tree count of 4431 .
After the undo the tree count at ply 2 is 4437 !!!

Does somebody has an explanation for this. I think that somewhere
a variable is uninitialised !!!

This is more important than it seems at first sight
because after the undo, gnuchess sometimes plays a much better move !!!

I discovered this while implementing a better null move heuristic
and some search extensions. These look very promising but before I
release the diffs I would like to solve this problem....


Tom
===============================================================================
Tom Vijlbrief
TNO Institute for Human Factors		Phone: +31 34 63 562 11
P.O. Box 23				Fax:   +31 34 63 539 77
3769 ZG  Soesterberg			E-mail: tom@izf.tno.nl
The Netherlands