Understanding StockFish output

Hello all!

I have recently begun using the chess engine StockFish to analyze my games.  I gather that it is quite popular and thus I assume many of you understand how it scores games and moves.

I understand the scoring system - kind of. I get that +(1.5) means white is essentially up 1.5 pawns, and likewise -(1.5), black.  However, I have an analysis now that looks like +(1.71)--.  What does this mean?  The game I am analyzing, I was playing as white, so I gather this means that I am up 1.71 pawns.  But I don't get what the -- means.

Can someone explain what -, --, +, and ++ mean?  Thanks a lot.

I don't get it at all but I am going to post in here so I remember to come back when somebody explains

I too would like to know this!

++ means white has a decisive advantage.

+ means white has the upper hand.

- means black has the upper hand.

-- you can probably figure that out by now.

I also don't know. Maybe the GUI (chess program) is doing it. What GUI are you using?

Dale, I don't think that's the case. I entered some ridiculous moves where white has a huge advantage*, and the ++ and -- switch back and forth as the analysis spins.

* 1. e4 h5 2. Nf3 a5 3. Nc3 a4 4. d4 h4 5. Be2 Rh7 6. O‑O Nh6 7. Nxh4 Ng8 8. Nf3 Rh8 9. Bf4 Rh7 10. Ng5 Rh8 11. d5 Rh7 12. Nxh7

Here's a link discussing the signs.

http://www.chessinformant.rs/system-of-signs/

Don't get hung up on what +1.71 means versus +1.50, etc.

Fugazy_Crapov, Stockfish is not doing the typical +-, +=, etc. symbols. It's doing "--" and "++", which I think is something particular to this engine.

Looks like http://www.talkchess.com/forum/ would be the place to ask, but I'm having trouble registering on that site.

What's your GUI?  Chess engines don't produce nuanced evaluation output.  They report plus or minus scores.  Some GUI's will add more elaborate symbols or comments.  The Shredder GUI will even display messages such as "+4.21 means white has a decisive advantage."  But these symbols and messages are from the GUI, which is interpreting and expounding upon the engine output.

In any event, I'm not seeing the inexplicable output you describe, so perhaps a screen shot of the output will help.  It's possible, I suppose, that a given GUI might display flawed output due to a bug or a non-standard UCI implementation in Stockfish.  But it looks fine from here.  If you're  running Windows, try the Tarrasch GUI.  It displays basic output only, near as I can tell.

http://www.triplehappy.com/

Here's an example of the "--" showing up:

http://i.imgur.com/jl8XEj6.png

This is from the official Stockfish Mac app.

Okay, I found an answer on reddit r/chess:

"When an engine (stockfish or other) writes ++ or -- after the evaluation number, in the analysis window of your user interface software, it means the latest mainline it has considered during the search process it's performing in the possible moves' tree is significantly better for White (++) or Black (--) then the evaluation value calculated for the previous mainline."

From: http://www.reddit.com/r/chess/comments/209xvm/could_someone_who_knows_about_the_stockfish/cg18we7

Good work!  I was going to suggest you just consider those symbols "noise."  I see those types of symbols in some GUI's (e.g. Fritz) but not in others.

Well, one thing that guy on reddit points out is you can use those symbols to tell when the engine has "settled down" in its analysis. If you're still seeing wild swings in evaluation, you should let the engine run longer. But if you haven't seen one of those ++/-- in awhile, you're probably safe that it's settled on the best move (or are at least close).

Good point.  I ended up learning here, too!

I would like to know what MN stands for in the stockfish output.... as i let it sit the number keeps raising right now its saying 18022 MN anyone know what that means?

I'm using stockfish 4 with SCID vs PC.Sample line below:

9 [-0.50]  6.... Be7 7.Bxe7 Ngxe7 8.dxc5 Qc7 9.Nbd2 O-O 10.Be2 Ng6 11.O-O Ncxe5 12.Nxe5 Nxe5  (0.03)

Can someone explain whether the 9 at the beginning has any significance other than the being the 9th variation examined? It doesn't number consecutively and often will skip, say from 9 to 14. Are 10-13 variations that are so bad they are discarded?

And the numbers in brackets (0.03) at the end? They start off at (0.00) and rapidly increase with each variation. Numbers like (346.06) are not uncommon in the last lines.

Is there a FAQ on stockfish somewhere that explains all this? The stockfish site doesn't.

What's most important us understanding how algorithms work. Points assigned by squares as related to position and piece points on the board. This algorithm pairs that number crunching with games in the database. Don't assume that a computer has it all figured out. Positions coupled with strange point sacrifices dont fit in the algorithm, and if you are good enough you can break the machine.

After nearly 5 years (post #11, Nov 2015), this fish is starting to smell . . .

What does M-1 mean