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Up Topic Rybka Support & Discussion / Aquarium / Strange IDEA behavior
- - By Chestman (*) [us] Date 2017-12-07 00:01
After running Aquarium for a file, I have thousands of positions in tree.

It's a fairly static position. All of a sudden, instead of showing the usual +.17 or whatever, I see +1.26 or so. What for? For a random Rook move that does not do much, and when I click on the move to see why, it shows a ?? move by the other side, giving up a piece for a pawn, and no other move, and of course after the blunder, the first side is way ahead.

Running 6 instances of Stockfish 8 engine.

Why would it minimax like this all of a sudden?

Running Build 950.
Parent - - By pawnslinger (***) [us] Date 2017-12-07 06:34
This sort of behavior is common.  You must continually be on guard for this.  I do this by routinely going thru the recommended line and firming the analysis at each step along the way (adding alternatives for the most part, to insure it doesn't get stuck on a dumb blunder, like you described).
Parent - - By Chestman (*) [us] Date 2017-12-08 23:19
I can be on guard for it on ply 0. But what if it happens somewhere 3-4 ply down? I'll never see.

Why does this happen?
Parent - - By dickie (**) [gb] Date 2017-12-09 10:12
It possibly happens where the engine is given a relatively short time interval or low depth target. If you look up the position in your IDeA/Results project epd file you will find the time used by Stockfish, the depth achieved and the extended pv. It is the engine's poor evaluation that creates the anomaly. Usually IDeA resolves the problem automatically and pretty quickly by tasking an alternative.

Press the function key F4 to add the "best line" to your notation. Then you will be able to see a number of plies ahead.
Parent - By pawnslinger (***) [us] Date 2017-12-09 16:10
It happens at any depth.  I have seen it happen at 16 ply depth and at 29 ply depth.  I think it is a bug in either Aquarium or the engine (I have seen it in several different engines).
Parent - By pawnslinger (***) [us] Date 2017-12-09 16:09
I constantly navigate thru the tree to find this at other than ply 0 (as you say).
Up Topic Rybka Support & Discussion / Aquarium / Strange IDEA behavior

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