49 votes
Accepted

Why does Stockfish undervalue pawns when compared to the classical "a piece is worth three pawns" approach?

I am not an expert on stockfish source code, but my understanding is the following. Humans: It is true, that the 1 piece equals 3 pawns approach is pretty accurate, surprisingly so. However as you ...
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  • 20.4k
37 votes
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Should a chess engine be aware of opposite-side castling?

I'm pretty sure Stockfish doesn't have explicit code that handles opposite-side castling. What it does have is: Some kind of "menace" score for enemy pawns advancing against our king. The ...
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  • 22k
28 votes

Is this a draw despite the Stockfish evaluation of −5?

This is a fortress and a draw. The black king can't advance as the rook, shuffling between h3 and f3, prevents it. The only way to break the fortress is to trade the queen for the rook and pawn, but ...
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  • 5,131
26 votes

Is chess a zero sum game?

When I said chess is a zero sum game in that answer, I wasn't referring to anything involving ratings. Obviously if we include ratings then chess isn't strictly a zero sum game, since the gains and ...
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23 votes
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Why does Fritz prefer underpromotion in this position?

It's because 1. exf8=Q+ Kxh7 2. Rxd7?? would be stalemate. I think it is a even a theoretical draw after 1. exf8=Q+ Kxh7 2. Qg7+. Therefore 1. exf8=B+! (with check!) is better, since white then can ...
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22 votes
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Is there an easy way to detect a draw in a King + Pawn vs King endgame?

There is a very easy way to detect whether King and Pawn endgames are drawn or not. This method I use is a very easy to understand one from Karsten Mueller and Frank Lamprecht's excellent book ...
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  • 2,247
22 votes

Is this a draw despite the Stockfish evaluation of −5?

This position is a standard classical fortress. There is no way the Black color can go through as long as White just shuffle pieces, wait and do nothing silly. Stockfish is a computer algorithm, it ...
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  • 21.6k
20 votes
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How do chess engines decide which best line to play when the game outcome is within their horizon?

If the engine can choose between getting mated in 2 or mated in 3, it'll choose the line where it is mated in 3 (even though the mate in 2 might be 'more difficult' to spot for humans). It can't ...
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  • 23.9k
20 votes

Is there an engine evaluation technique that factors in 'time'?

Is there any established system for evaluating positions taking into account time for both players? No, there isn't. This is for two main reasons: There is no objective measure for how time affects ...
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  • 77.5k
20 votes
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Does blitz change the relative value of position vs material?

It just seemed obvious to me that gambits would work better with faster games, for the same reasons as given in the comments - it's harder to defend than attack, etc. I tried looking at several ...
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  • 15.6k
19 votes
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Why is this position in the 3.d4 d5 Petroff equal?

What I can't wrap my head around is that Stockfish says that this position is completely equal. Why is that? Black has the bishop pair in a completely open position (no center pawns). This advantage ...
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  • 77.5k
18 votes
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Why is 11. .. h6 such a bad move?

By playing 11...h6, you created a weakness on g6, and you created a target on h6, now it is easier for white to open up a position around your king by pushing their g-pawn. White also has a potential ...
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  • 6,497
17 votes
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How are the scores decided in Chess?

Those aren't scores; there are just three possible scores in chess: White wins, Black wins, and draw. Those are evaluations of the chess engine; a score of +0.62 means the engine thinks White's ...
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  • 23.9k
16 votes
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Stockfish: What is the maximum (minimum) centipawn score that a position might be evaluated at?

The best way to normalise a centipawn score to [-1,+1] range is using a sigmoid function, as that closely approximates the likelihood of a given centipawn advantage converting to a win, and avoids the ...
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  • 1,659
16 votes

Should a chess engine be aware of opposite-side castling?

Interesting question. I think it depends on how much bottom-up intelligence the engine has. For example, AlphaZero was given no explicit heuristics, but was able to infer plenty of strategy by playing ...
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15 votes

Is chess a zero sum game?

Chess is a zero sum game. There is 1 point available and it is divided over the players, what one gains the other loses. It is a simple concept with a simple answer. Tournament rules mention some very ...
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  • 26.3k
15 votes

How would the min max algorithm of a chess engine work in the case of 3 player chess?

The problem is really not in chess, but in any naive 3-player version of any 2-player strategy game. In general, it is hard to make an interesting 3-player game where each player's performance is ...
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  • 2,473
13 votes
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Why is this position considered to give white a significant advantage?

[FEN "r4rk1/2p1qppp/1p3n2/p7/2B4B/4P3/PPQN1Pbb/2KRR3 w - - 0 1"] 1. f3 {traps the bishop} Rad8 2. Re2 Bxf3 (2...Bd6 Rxg2 Kh8 Rh1 {the Black king is not safe at all}) 3. Bxf6 Qxf6 (3...gxf6 ...
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  • 3,450
12 votes
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How do chess engines evaluate a position if the position is in the middle of an exchange?

A good chess engine won't stop after a predetermined number of moves, but will keep looking until the position is "quiescent", which roughly speaking means that there are no pending captures or checks....
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  • 10.3k
12 votes

Why is 11. .. h6 such a bad move?

To add to the existing answers, you just gave up your light squared bishop for no apparent reason, while creating many light square weaknesses around your king with the same move! Now white is the ...
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  • 296
11 votes
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Why does Stockfish suggest capturing a bishop in this position when my opponent can fork my king and rook?

White does indeed fork the king & rook after Nc7+ - but after Nxa8, the knight is not escaping, so Black is at worst even on material. [FEN ""] 1. d4 c5 2. Nf3 cxd4 3. Nxd4 Nc6 4. Nc3 e5 5. ...
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  • 22k
11 votes

Why does Stockfish suggest capturing a bishop in this position when my opponent can fork my king and rook?

I agree with the other two answers, but I feel like I also need to comment on the beginning of the game since there was A LOT more important stuff there than just the answer to why Qxg5. This is very ...
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  • 32.1k
10 votes
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Oscillating Stockfish Evaluation on Laptop

If I understand correctly your x axis is the moves. Your script implied Anand and Prag were blundering every time they make a move, Clearly you have a bug in your script. Stockfish engine always give ...
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  • 21.6k
10 votes
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Queenless Imbalanced Middlegame

First, I don't think that there is any doubt that black has significant compensation, but clearly, black is still trying to hold this, not win it when talking two computers playing each other. I ...
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  • 32.1k
10 votes

Why does Stockfish undervalue pawns when compared to the classical "a piece is worth three pawns" approach?

Please note that those values are "abstract", later to be modified by the specifics of the position. For example, even though a knight appears 0.8 pawns less valuable than a bishop, it could be that ...
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  • 13.2k
10 votes
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Lichess endgame evaluation

Unless you explicitly hard-code these endgames, or provide the computer with endgame tablebases, they will apply what they've always done throughout the game: search lines and return the static eval (...
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  • 22k
10 votes
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How come it's actually Black with the advantage here?

White's actually quite close to busted in that position after 16...Qd5. Of the two points you bring up, note that White doesn't actually control the e-file because Black is ready to play a rook to e8 ...
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  • 22k
10 votes
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Why is this "slow move" with the king a good move?

Just because Stockfish thinks a move is best doesn't mean it is best. But let's see why Stockfish might like it. When I look at Stockfish's static evaluation of that position, and move the king from ...
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  • 15.6k
10 votes
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Why is h4 much better than h3?

Why is h4 much better than h3? It's very simple. The prospects for the bishop are much better on g3 than h2. On h2 the bishop does nothing useful and it will take a lot of moves to get it back into ...
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  • 77.5k
10 votes
Accepted

Why is this seemingly quiet and normal position actually -3?

You mentioned seven points which give Black an advantage. Here are two more: White has a bad bishop, blocked by its own pawns on c4 and e4. Conversely, Black's bishop is good. Black is more ready for ...
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