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In a recent game I swapped off a knight for 3 pawns:

[Event "County Match"]
[Site "Deepest Darkest Southern England"]
[Date "2018.01.20"]
[White "English Player"]
[Black "Ian Bush"]
[Result "0-1"]
[FEN ""]
[StartPly "41"]

1.c4 Nf6 2.Nf3 g6 3.g3 Bg7 4.Bg2 O-O 5.O-O d6 6.Nc3 c5 7.a3 Nc6 8.Rb1 Bf5 
9.d3 Nd7 10.Nd5 Nb6 11.Ne3 Bd7 12.b4 Qc8 13.b5 Nd4 14.Nxd4 Bxd4 15.a4 Bh3 
16.a5 Bxg2 17.Kxg2 Bxe3 18.Bxe3 Nd7 19.Bh6 Re8 20.Qd2 Nf6 21.h3 Qf5 22.e4 
Nxe4 23.dxe4 Qxe4+ 24.Kh2 Qxc4 25.Rfe1 Rad8 26.Re3 f6 27.Rbe1 e5 28.Rd3 
Re6 29.Rc3 Qxb5 30.Qd5 Rde8 31.Rb3 Qc6 32.Qxc6 bxc6 33.Rb7 R6e7 34.a6 Kf7 
35.Be3 Ke6 36.f4 Rxb7 37.axb7 Rb8 38.Rb1 a5 39.fxe5 fxe5 40.Kg2 a4 41.Kf2 
a3 42.Ke2 a2 43.Ra1 Rxb7 44.Rxa2 c4 45.Kd2 d5 46.Kc3 Rb3+ 47.Kd2 d4 48.Bf2
Kd5 49.Ra5+ Ke4 50.Rc5 c3+ 51.Kc1 d3 52.Rxc6 d2+ 53.Kc2 Rb2+ 54.Kd1 Rb1+ 0-1

I've started here as this was the plan after Qf5, and I played this way as I thought it a good way to get winning chances - it was a match and as it all looked fairly even wins were the order of the day. But Stockfish really doesn't like it, putting me down ~1.5 pawns, and I don't really understand why. Can somebody turn the "thoughts" of the metal monster into human terms for me?

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5
  • 1
    Can you please post the lines by Stockfish? Including SF's top line suggestion? The question is only answerable if we have the engine outputs.
    – SmallChess
    Commented Jan 21, 2018 at 12:53
  • When you said "down 1.5", do you mean -1.5 score??
    – SmallChess
    Commented Jan 21, 2018 at 12:54
  • 2
    Is your q. about Stockfish or about the position, say after 24... Qxc4--? I don't know about Stockfish, but I feel that white has a huge advantage, perhaps a winning advantage.
    – Wlod AA
    Commented Jan 22, 2018 at 2:28
  • 1
    Have you asked Stockfish why it doesn't like it? Meaning have you tried to see the follow-up variations from this position upto a reasonable depth? Engines are all about concrete play, so to understand them it's best to simply go through its suggested variations in order to understand why. If the variations are still unclear to you, then include them in your post and people will be able to help you a bit better.
    – user929304
    Commented Jan 22, 2018 at 12:53
  • (on a side note, 17...Bxe3 doesn't look right at all)
    – Evargalo
    Commented Mar 6, 2018 at 8:50

2 Answers 2

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8

Counting material is only one portion of evaluating a position. Stockfish considers space, piece mobility and activity, king safety, etc.

All of that produces an evaluation of the position, and for this one SF grades it (using LiChess) as about +2.2 (depth 31).

I note that before your knight sac Stockfish thinks you were already down by about 1.2, despite roughly equal material. That bishop on h6 controlling your weakened dark squares, for example, is clearly worth more than your knight.

As for your decision to sac the knight, from a practical point of view it seems a reasonable choice in a bad situation, because if you simply move your queen to e6 or e5, as SF suggests, white has a clear and natural plan of f4 followed by eventually opening up that file, and your clumsy rooks will not be nimble defenders.

SF suggests for white an immediate b6 after your queen takes on c4, and with that you will not get the pawn storm as you did in the game. White will have an open line to invade with his rooks (which one depends on your reaction to b6) and his extra piece will tell.

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  • What does the engine do after 25.b6 a6 ? It seems to me that White's position is not that easy at all to play. The bishop should be better than the pawns, but Black has an easy plan (his only possible plan, e5, d5-d4, c4-c3...) but to prove it White will have to open lines on the kingside with h4 or (maybe best) f4, and that opens his own king a bit. Not so easy to handle !
    – Evargalo
    Commented Mar 6, 2018 at 8:49
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    Sorry @Evargalo, didn't see this comment before. After b6 a6 SF10(now, was SF8 before) says white is crushing after f4 (actually Rbc1 first followed by f4). White opening up his own king is not really a big concern because black can't mobilize. As an exercise I played it out myself as white against SF10 and managed to win despite some mistakes on my part.
    – Paradise Pete
    Commented Jan 10, 2019 at 8:32
-2

Well, sometimes knight are useful to fork pieces and stuff, but 3 of your pawns for a knight, in this position, is bad because now black has two connected passed pawns that could be put into good use during the endgame.

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    Please have another look at the question. The OP has black, and Stockfish likes White's position.
    – Glorfindel ♦
    Commented Mar 6, 2018 at 8:18

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