Stockfish 18 fails to deliver a checkmate in 4 moves!

A few days ago, I was solving some tactics puzzles on another chess platform including the following one. Black is down a whole rook here and therefore needs to act quickly and decisively.

https://lichess.org/study/eN8YnZCh/D2Ms26A2#0

I solved this puzzle in about four minutes. The possible checkmate moves are obvious: Nc2 or Qxb4 or Pxb4. It seems White has control of both squares until you realize that a potential blocking piece on d2 would disrupt White's coordination.

So I played:

... Qxb4+
Bxb4 Rd2!!
Qxd2 Nc2+
Qxc2 axb4#

I then analyzed the position with Stockfish and was somewhat shocked that the engine couldn't find the move 1... Qxb4+ even after considerable thought!

Even after ten minutes, it only showed the variation 1... Nxd1, which gives Black a slight advantage of -0.3.

How is that possible, I ask you?

A few days ago, I was solving some tactics puzzles on another chess platform including the following one. Black is down a whole rook here and therefore needs to act quickly and decisively. https://lichess.org/study/eN8YnZCh/D2Ms26A2#0 I solved this puzzle in about four minutes. The possible checkmate moves are obvious: Nc2 or Qxb4 or Pxb4. It seems White has control of both squares until you realize that a potential blocking piece on d2 would disrupt White's coordination. So I played: 1. ... Qxb4+ 2. Bxb4 Rd2!! 3. Qxd2 Nc2+ 4. Qxc2 axb4# I then analyzed the position with Stockfish and was somewhat shocked that the engine couldn't find the move 1... Qxb4+ even after considerable thought! Even after ten minutes, it only showed the variation 1... Nxd1, which gives Black a slight advantage of -0.3. How is that possible, I ask you?

IamNOTamod

When I turn the engine on it immediately shows #-4...

Tenakel

@IamNOTamod said ^

When I turn the engine on it immediately shows #-4...

Oh, really?

Could it be my computer's weak performance?

Or do I need to change some settings in SF18?

@IamNOTamod said [^](/forum/redirect/post/Ko03u4p8) > When I turn the engine on it immediately shows #-4... Oh, really? Could it be my computer's weak performance? Or do I need to change some settings in SF18?

TheMagnusAura

What? Where?

![image.png](https://image.lichess1.org/display?fmt=png&h=0&op=resize&path=6mlUDfCgFCka.png&w=864&sig=c4a8ccc6c965bcc92c82a789723dbf7a2a451022) What? Where?

nomismatongambit

If this is literally 2 days ago, I also found at that time that Stockfish was just not working properly on lichess. It was missing very obvious things but it wasn't down to not searching deep enough. I can only imagine that was some sort of glitch on the server. It only lasted for a few minutes or so.
If you were using a separate Stockfish and NOT running on the cloud this of course shouldn't apply to you.

If this is literally 2 days ago, I also found at that time that Stockfish was just not working properly on lichess. It was missing very obvious things but it wasn't down to not searching deep enough. I can only imagine that was some sort of glitch on the server. It only lasted for a few minutes or so. If you were using a separate Stockfish and NOT running on the cloud this of course shouldn't apply to you.

Toscani

edited

python3 solve_fen.py
fen = "k2r4/1p3p2/n1bqp1p1/p7/1Pp1PP2/K1B1nNP1/PP2RN2/3RQ3 b - - 0 1"
Depth 1: +62
Depth 2: +62
Depth 3: +62
Depth 4: +62
Depth 5: +62
Depth 6: +62
Depth 7: +62
Depth 8: +74
Depth 9: +48
Depth 10: +60
Depth 11: +39
Depth 12: +34
Depth 13: +26
Depth 14: +17
Depth 15: +18
Depth 16: +21
Depth 17: +26
Depth 18: +34
Depth 19: +39
Depth 20: +45
Depth 21: +28
Mate detected at depth 22: mate in 4

python3 solve_fen.py fen = "k2r4/1p3p2/n1bqp1p1/p7/1Pp1PP2/K1B1nNP1/PP2RN2/3RQ3 b - - 0 1" Depth 1: +62 Depth 2: +62 Depth 3: +62 Depth 4: +62 Depth 5: +62 Depth 6: +62 Depth 7: +62 Depth 8: +74 Depth 9: +48 Depth 10: +60 Depth 11: +39 Depth 12: +34 Depth 13: +26 Depth 14: +17 Depth 15: +18 Depth 16: +21 Depth 17: +26 Depth 18: +34 Depth 19: +39 Depth 20: +45 Depth 21: +28 Mate detected at depth 22: mate in 4

Tenakel

edited

Thank you all for the feedback.

After changing the depth in the engine settings, SF now shows me checkmate very quickly as well.

Thank you all for the feedback. After changing the depth in the engine settings, SF now shows me checkmate very quickly as well.

Tlilchantli

This is intense. The rook move to d2 is very deep. That must be normal for y'all in the 2000 big league.

NM MrPushwood

Yeah, that was certainly an act of genius. :)