63 votes
Accepted

Is Stockfish 11 (level 20) beatable?

The answer is that they either played it on some very handicapped mode, they took back A LOT of moves, or they are probably lying. Stockfish 11 is currently rated about 3607, and that is in standard ...
  • 32.1k
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 ...
  • 20.5k
42 votes

Is Stockfish 11 (level 20) beatable?

It's absolutely beatable, but not by an unassisted human. Anyone who claims to have done so is either lying or stacked the deck super heavily in their favor (e.g., by having Stockfish search only to ...
  • 22.6k
37 votes

How is Alpha Zero "more human"?

Page 5 in the paper has your answer: ... AlphaZero compensates for the lower number of evaluations by using its deep neural network to costs much more selectively on the most promising variations - ...
  • 21.6k
33 votes

Stockfish is considering a move in a book by GM Mihail Marin as a blunder

Mihail Marin simply missed that 1.Ng6 is winning, even faster than 1.Qg6. During opening analysis, and even during a game, sometimes when you find a satisfying continuation you forget to follow Lasker'...
  • 13.1k
28 votes
Accepted

Stockfish blunders away a piece

This is not a blunder, expected behaviour from the engine. Everything worked as intended. Try to copy the FEN string out, and you'll know. Although the position looked winning, White didn't have ...
  • 21.6k
28 votes
Accepted

Why is exchanging the queens bad in this position?

I think it is because 21.Rfc1 wins the c7 pawn. If black responds with a queen trade, she can't defend the pawn on c7 because white's bishop can attack a defending rook on c8 or d7. [White "NN"] [...
  • 26.4k
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 ...
  • 5,131
27 votes

How to install stockfish on ubuntu?

Just for completeness, I would like to add more explicit instructions for using stockfish in Scid, because sometimes it is a little confusing how to get stockfish to function in an actual chess ...
27 votes

Bad Stockfish evaluation

Stockfish isn't a perfect chess-playing entity, and you've found a position where it's unable to tell is a draw (at least until the 50 move rule kicks in and helps it prune). These positions are ...
  • 22.6k
27 votes
Accepted

Why does Stockfish suggest h4 here?

The main idea is to try to trap the c2-bishop. After h4 White is threatening to play Rc1 and black can't save the bishop. That's why black should play ...h5 giving their bishop a retreat square. Note ...
  • 948
26 votes

Why doesn't Lichess' Stockfish suggest this bishop sacrifice?

Good question. I let Stockfish 11 think on the position, and even by around depth 25-26 it didn't suggest Bf6. But like in your case, after making the move on the board, Stockfish suddenly realizes it ...
25 votes

Would an ensemble of chess engines beat the best one?

The answer is "No". If you have a defined fixed set of resources - CPUs, memory, cache, etc. - and you allow one engine to have full use of them then that engine is going to be able to ...
  • 81k
24 votes
Accepted

Understanding AlphaZero

How does AlphaZero select a move in the search? This is very obvious from the paper. Each simulation proceeds by selecting in each state s a move a with low visit count, high move probability and ...
  • 21.6k
24 votes
Accepted

Hardware used in AlphaZero vs Stockfish match

That's why I wonder whether there have been any attempts made to provide comparable hardware to both. This is Google you're talking about! So the answer is obviously "No". From the original paper ...
  • 81k
24 votes

Why is exchanging the queens bad in this position?

It is true that Rfc1 wins the c7 pawn, but even if that where not the case, Rfc1 is significantly better technique than initiating the exchange yourself. The black queen is pinned against the king, ...
24 votes
Accepted

How does Stockfish know if the king is in check?

If you're curious about the Stockfish code, it can be found here: si->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove); We call the attackers_to method to ...
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 ...
  • 21.6k
21 votes
Accepted

Which is better-Stockfish 10 or AlphaZero?

We can't say for sure since AlphaZero is a private engine, i.e. we don't have games between it and the latest versions of Stockfish. Still, if AlphaZero hasn't improved since it was unveiled, it will ...
  • 22.6k
21 votes
Accepted

Three way fork-Why take the rook instead of the queen?

Both moves lead to crushingly won positions for White, so all things considered it doesn't matter which one you choose. For me, Stockfish shows +14 for Nxg8+ and +9 for Nxd7. The difference between +9 ...
21 votes
Accepted

Did Stockfish regress from October to December 2020? If so, why?

It is of course always possible that Stockfish did regress. The way changes are tested for Stockfish, or most engines for that matter, always allows for regressions to pass some of the time. (you ...
  • 2,580
19 votes

How is Alpha Zero "more human"?

Most strong engines emphasize looking very deeply, at the expense of having a superficial evaluation function. In the AlphaZero paper, they say that Stockfish looks at 70 million positions per second. ...
  • 26.4k
18 votes
Accepted

Do Stockfish and the tablebase work together or independently?

play the game until six pieces Stockfish doesn't do that, that's not what tablebase is for. Briefly, tablebase boosts engine search well before six-men position reached on the board. Let's do an ...
  • 21.6k
18 votes

How does Stockfish know if the king is in check?

Where and how in Stockfish's code is check detected? This is simple engine programming. You will need to build a bitboard of the attacking squares and two bitboards of your king, one for each color. ...
  • 21.6k
17 votes
Accepted

Returning scores for all possible moves from a chess engine

Of course there's a way: I'm going to show you one way of doing it on your own, using only free software. We'll write a small script in Python (I'm using v2.7) and only use the wonderful python-chess ...
  • 11.9k
16 votes
Accepted

Why are Leela's fans so passionate?

You can't really objectively answer this question, but I'll share my view. One of the important factors to take into account is that Leela Chess Zero project requires tremendous computational ...
16 votes
Accepted

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 ...
  • 1,659
16 votes

Would an ensemble of chess engines beat the best one?

No, an ensemble of chess engines won't beat the best one. The reason is simply because of hardware. Let's take the strongest CPU engines right now to keep things simple. These are Stockfish, Komodo, ...
  • 22.6k
16 votes

What does it mean when stockfish evaluates a move as an inaccuracy after previously thinking it was the best move?

Don't read anything into it. This is the fault of chesscom's poor interface and has no deeper meaning. Every other website I know of does not have this issue. You should trust the current evaluation ...
  • 5,575
15 votes

Solvable studies that computers fail to crack

Here is an outrageous mate in 57 puzzle which none of the top 3 engines are able to solve: [fen "8/6pp/5p2/k7/3p4/1Q2p3/3prpp1/3Kbqrb w - - 0 1"] 1.Qc4 Kb6 2.Qd5 h6 3.Qc4 Ka5 4.Qb3 h5 5.Qc4 Kb6 6....
  • 3,043

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