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Up Topic The Rybka Lounge / Computer Chess / How do programs decide what move to make between 0.00 lines?
- - By rocket (****) Date 2020-09-26 11:11
What mechanism ultimately decides which one it's gonna be? It would seen arbitrary, yet chess engines operate on the very opposite of arbitrary decisions.
Parent - By Eelco de Groot (***) Date 2020-09-27 06:40
In most implementations of alpha beta that I have seen, you only change the best move if it is 'really' better, so it has to have a higher score. Changing moves comes at a cost, because you have to calculate a new PV, that takes time, memory and the PV calculation may turn out to be a false Fail High, then all the effort is more or less wasted. Rybka in early days I believe, Vas has posted about this, had a mechanism where a new move did not only have to be higher, but significantly higher evaluation, to counteract the false Fail Highs. All a matter of tuning in classical Alpha Beta programs.
Parent - By Vegan (****) Date 2020-09-30 04:10
chess engines all have the same problem, evaluating a given position 

so building a tree to check for an optimal position goes back to the evaluation logic
Parent - - By user923005 (****) Date 2020-09-30 05:46
If there are two 0.00 lines, it is most likely drawn.
Something you can do is try other engines.
If SF can't make up his mind, try LC0 (if you have a nice GPU).
Komodo sometimes has interesting ideas, and I have a newfound fondness for Shashchess.

In the end, you will probably be stuck with choosing between several zero lines, so I would suggest choosing the one most appealing to you.
As yourself, "Which one of these lines woudl *I* rather play, if there were no computer involved."
Often, our intuition in such things can be very good.
Parent - - By h.g.muller (****) Date 2020-10-13 13:06
If there are two (or more) 0.00 lines, the engine would never know it. Which one it discovers first is purely governed by chance. And after that, the only thing it does is prove that the remaining moves do not score better than 0.00. As soon as it has proven that, it does not go on to demonstrate the true score is actually -900, it doesn't care.
Parent - - By user923005 (****) Date 2020-10-13 17:19
My language was imprecise.  I did not mean to imply the existence of two drawing lines.
If there were two initial evaluations of 0.0 for the score after some timed search, both of those can be wrong.
It is not terribly unusual for SF to have an eval of 0.0 for quite a while and eventually find checkmate.
Parent - By Vegan (****) Date 2020-10-15 23:04
some engines will search more deeply with quiescent positions looking for an edge
Up Topic The Rybka Lounge / Computer Chess / How do programs decide what move to make between 0.00 lines?

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