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Subject: Gnuchess bug when opponent is out of time

Author: Axel Boldt

Date: 23:25:23 04/01/99


Hi,

I often play gnuchess without paying attention to my time. I noticed
that there's a bug in the program which shows up in certain positions
when I'm out of time.

This is even reproducible (gnuchess 4.0 pl 79): Start xboard (or
gnuchessn with 5 minutes for 40 moves in "hard" mode so that it thinks
on your time; xboard puts gnuchess automatically in this mode), go to
Mode|Edit Game, and set up the following game:

  1. e4 c6
  2. d4 d5
  3. Nc3 dxe4
  4. Nxe4 Nf6
  5. Nxf6+ gxf6
  6. Bc4 Rg8
  7. Qh5 e6
  8. Ne2 b5
  9. Bd3 Rxg2
 10. Be3 e5
 11. 0-0-0

Now start the computer as black (in gnuchessn, say "hard" then "black"
then "go", in xboard go to Mode|Machine Black). It will move

 11. ... Bg4

Now wait about 10 minutes so that your time is at -5 minutes, then
move

 12. Qxh7
The computer will now answer either

 12. ... Bc5??

or

 12. ... Kd7??

If you do not wait for 10 minutes (or gnuchessn is not in "hard" mode,
or xboard was started as "xboard -xclock"), then it will move either

 12. ... Bf3

or

 12. ... Qd5

both of which are clearly much better.

Is anybody familiar enough with the gnuchess internals to venture a
guess what could be wrong?

Thanks,
   Axel

--
 Axel Boldt  **  axel@uni-paderborn.de  **  math-www.uni-paderborn.de/~axel/
 Sponsor free software at the Free Software Bazaar visar.csustan.edu/bazaar/




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