Ethereal: suboptimal moves in won endgame

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ernest
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Ethereal: suboptimal moves in won endgame

Post by ernest » Sat Sep 15, 2018 3:04 pm

This is a follow-up of my previous thread concerning the CCCC game #450, Nemorino-Ethereal
http://talkchess.com/forum3/viewtopic.php?f=2&t=68438

I am always appalled when I see a good program, here Ethereal, play a sequence of "stupid" (or very suboptimal) moves.
This was the case in an easily won endgame.

Maybe it shows an anomaly of Ethereal (access to Syzygy, or...) or a problem of CCCC (the game ended abruptly after move 83).

See moves around 65 to 80. :shock: :roll: :evil: :mrgreen:

Thanks to Guenther, I was able to find the pgn in https://newman.chess.com/games.pgn


AndrewGrant
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Re: Ethereal: suboptimal moves in won endgame

Post by AndrewGrant » Sun Sep 16, 2018 2:18 am

ernest wrote:
Sat Sep 15, 2018 3:04 pm
This is a follow-up of my previous thread concerning the CCCC game #450, Nemorino-Ethereal
http://talkchess.com/forum3/viewtopic.php?f=2&t=68438

I am always appalled when I see a good program, here Ethereal, play a sequence of "stupid" (or very suboptimal) moves.
This was the case in an easily won endgame.

Maybe it shows an anomaly of Ethereal (access to Syzygy, or...) or a problem of CCCC (the game ended abruptly after move 83).
I went and stepped through the PGN with Ethereal running Analysis. It looks odd, but I don't think this is really an issue, on my part, or on CCCC's part.

If I'm reading the PGN correctly, there was 1, maybe more, single depth moves from Ethereal. That explains some of the moves, but not most.

Ethereal is known to repeat a position twice, when in the process of working out final solution. Furthermore, engines in general can make very strange moves when faced with a position that is a guaranteed win. Every line Ethereal played there still maintains a TB win.

Conclusion: Seems odds, but not a cause for concern in my view.

ernest
Posts: 1798
Joined: Wed Mar 08, 2006 7:30 pm

Re: Ethereal: suboptimal moves in won endgame

Post by ernest » Sun Sep 16, 2018 12:51 pm

AndrewGrant wrote:
Sun Sep 16, 2018 2:18 am
..........
Conclusion: Seems odds, but not a cause for concern in my view.
OK thanks, Andrew !

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