🚀 go-pugleaf

I'm just starting to take up chess programming as a hobby, which means
I'm a beginner, which means don't be too hard on me if my question is
stupid.


For some reason I pick up an older version of gnuchess (4.0 pl 17) to
start with.  The gnuchessr that I compiled gives me a strange result.
These are the bestlines when it starts from the beginning board without
opening book (running on a Sun SPARC 10):

Move# 1    Target= 11243    Clock: 900000
 1.     27    0       21   g1f3
 2.     11    0       81   g1f3  g8f6
 3&     29    0      144   g1f3  g8f6  b1c3
 3.     29    1      605   g1f3  g8f6  b1c3
 4&     12    1     1142   g1f3  g8f6  b1c3  b8c6
 4.     12    1     1946   g1f3  g8f6  b1c3  b8c6
 5&     21    2     3716   g1f3  g8f6  b1c3  b8c6  d2d4
 5.     21    4    10607   g1f3  g8f6  b1c3  b8c6  d2d4
 6&     13    7    23010   g1f3  g8f6  b1c3  b8c6  d2d4  d7d5
 6.     13    7    23029   g1f3  g8f6  b1c3  b8c6  d2d4  d7d5
 7-  -9992    7    23031   g1f3  g8f6
     ^^^^^ why??? -> *
 7&     20    7    23032   e2e3  g8f6
 7.     20    8    23038   e2e3  g8f6
 8&     21    8    23040   e2e3  g8f6
 8.     21    8    23046   e2e3  g8f6
 9&     22    8    23048   e2e3  g8f6
 9.     22    8    23054   e2e3  g8f6

* Why does it return that huge negative score?  If it encounters some
  deadly line, it should be cut-off by the alpha-beta search, shouldn't it?
 

When I run it on an ancient IBM RT (the first IBM UNIX workstation),
it gives me the same thing, only that -9992 score appears at 6& move.
After that -9992 score, the computer basically chooses a move as it
likes, sometimes d2d4, sometimes d2d3, and even f2f4.


How do you guys debug such an anomality?  I can't do it with a
debugger since it may take tens of thousands of search() calls before
it reaches that trouble spot.  The latest I found is that all the
return statements in search() return normal values (I think), but
suddenly the line
     node->score = -search (xside, ply +1, blahblahblah
returns
     node->score == -9992.
How do I proceed from here?  Thanks in advance.

--
                         Johanes Suhardjo (johanes@farida.cc.nd.edu)
--
CAUTION:  Improper use of your brain may cause damages and void the
          manufacturer's warranty.