Serious bug in Gothmog 0.2.6!

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Serious bug in Gothmog 0.2.6!

Postby Tord Romstad » 04 Aug 2003, 22:17

Geschrieben von: / Posted by: Tord Romstad at 04 August 2003 23:17:38:

I knew it was too early to release this thing. :-(
I have just discovered an extremely serious bug in the selective search, which
causes frequent and grave tactical oversights. I have already described the bug
in another post, but because that message is hidden deep within a long thread I
repeat it here.
The bug appears when the program encounters a position where the side to move
has a so bad position that all the available moves are pruned because none
of them is likely to bring the score anywhere near alpha. In such positions,
Gothmog concludes: "I have no moves, and I am not in check -- it's a
stalemate. Let's return 0". :-)
I don't know how often this occurs in practise, but I quickly checked my last
20 test games against Phalanx. At least three of them were decided by tactical
mistakes caused by this bug.
Strangely enough, this bug has been in my program since the beginning, and
remained undiscovered until now. I have noticed some really weird tactical
mistakes from time to time, but I was never able to locate the bug.
Linux and Mac OS X binaries of version 0.2.7 (where the bug is fixed) are now
available for download on the Gothmog homepage. A Windows executable will be
ready later this week.
Tord Romstad

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