19

I reached this position as Black:

[Title "Black to move"]
[FEN "8/8/8/3q4/6kp/7R/6P1/6K1 b - - 3 46"]

And I felt that I cannot make any progress and so it feels like a draw. However, Stockfish evaluates it as −5.1, though it also seems to be unable to get anywhere. So is this actually a draw, or is there some obscure line of play that Stockfish has missed as well?

19
  • 3
    I just want to confirm: the White pawn is on its starting square, and not one square from promotion, correct? – D M Mar 14 at 4:39
  • 8
    Are you per chance using a really old version of Stockfish? My current Stockfish gives an evaluation of -0.4, so basically a draw eval. Also, it being a 6 (or even if it was 7) piece position you can look up in the tablebase e.g. by setting up a position for the lichess analysis board: lichess.org/editor – koedem Mar 14 at 7:34
  • 1
    @koedem: Well I was using the Lichess analysis which supposedly uses Stockfish, but after your comment I realize that it could be due to Lichess' version not having a full endgame database... – user21820 Mar 14 at 8:30
  • 2
    @Allure it does indeed depend on the browser, e.g. my version of Firefox still has me use Stockfish 11. Basically the NNUE version of Stockfish requires some specific instructions in web assembly that not all browsers support yet, though hopefully that will change soon. – koedem Mar 14 at 21:24
  • 2
    @OscarBravo: Yes, that's what I prefer. And yes, there is a convention that shows the board from White's viewpoint regardless of the player to move, which I don't like when analyzing a single position. Obviously, from any one position it is clearly sensible to stick to the initial viewpoint throughout the moves. It would have been better if the board-viewer on Chess SE came with numbers and letters at the sides of the board, which would have eliminated all this unnecessary confusion! – user21820 Mar 16 at 15:18
3

A similar position featured in a MathOverflow answer on whether "high-level proofs" about chess positions are possible. A proof is outlined in that answer, hopefully enough to explain why it is a fortress.

28

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 the resulting endgame is still a draw.

3
  • weird question: do you have like a reference for this please? as to whether or not it's a draw, ok it's mathematics you don't quite need a reference. i'm hoping for a reference that explains it's a fortress – BCLC Mar 15 at 6:52
  • 7
  • 1
    I thought that the logical proof would be enough, but thanks the 2Ardweaden for providing the concrete answer. – Mike Jones Mar 16 at 15:27
22

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 has no intelligence. It doesn't know it's a draw unless it searches for all the possibilities, but it's practically impossible.

Connect to a 6-piece tablebase, and you will instantly see it's a draw. Or run Stockfish with a tablebase, instant draw.

2
2

This isn't anything special. Chess engines have also their capacities and are overevaluating some positions which are actually drawn.

For example, this position here is also about +4 but in reality, this is a draw.

[FEN "5r1k/K4bpp/8/8/1P1Q4/8/7P/8 w - - 0 1"]
5
  • Of course I know that engines make mistakes, otherwise I won't be asking my question in the first place just to check that I didn't miss something. Anyway, why don't you use the chess player feature on this site? – user21820 Mar 20 at 12:30
  • 2
    @user21820 You can't expect all newcomers to know about it right away. Next time, consider linking it for them. – Rewan Demontay Mar 20 at 16:03
  • @RewanDemontay: I didn't expect newcomers to know it; I was wondering whether Jagger didn't like the inbuilt chess player, so I asked. – user21820 Mar 20 at 16:10
  • SF12 evaluates this draw: 2b5/pb1b4/p1k5/p3K3/6b1/5b2/4b3/8 w - - 0 1 as -35. – Martin Rattigan May 27 at 17:44
  • And this draw: BNBKBNBN/NBNBNBNB/BNBNBNBN/NBNBNBNB/BNBNBNBN/NBNBNBNB/BNBNB1BN/NBNBkBNN w - - 0 1 as -151 (but I think the position is illegal). – Martin Rattigan May 27 at 18:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.