Fat Fritz analysis: A matter of technique

Insights into Anand's game

Like many readers here, I am foremost a chess player and chess fan, and I was enjoying the battles from the Sinquefield Cup with great relish, in spite of the disappointing number of games that failed to produce the deserved decisive result. One of the most thrilling games was just such a case: a near win by Vishy Anand over Ding Liren that ended in a draw.

Most players and pundits will remember the game mostly for the missed 26…♞e4!! which would have won the game on the spot. 

To be fair, while Vishy himself was undoubtedly gnashing his knuckles over this later that night, Ding Liren readily admitted in the post-game interview that he himself had not even suspected the move during the game.

When the gods disagree

However, there was a crushing move missed two moves earlier that was not mentioned by the commentators because they were fixated on the opinion of Stockfish. Here is the position two moves earlier after 24.f3. 

In this position, there wasn’t a lot of comment about Black’s choice 24…h5 as this was also Stockfish's choice, so feedback was along the lines of “he found the best move”. I sat up at this point because on my laptop, with a fairly middling GPU, I had been following the game with a beta of Fat Fritz, and it was practically chanting victory in the case of 24…♛c4!! 

Here is what I was seeing

In fact, Fat Fritz was to point out that ...♛c4 was a thematic play on more than one occasion after this, including when Anand played it during the game, though by then it needed very precise play to guarantee the win. After the game, I asked Anand about this, and he said that ...♛c4 was 'obvious technique', and as such was a move he analysed numerous times. 

The curious thing was that when I consulted Stockfish on my i7 processor, even after several minutes of analysis it ranked 24…♛c4 a distant third, just better for Black, but hardly crushing.

So now the question remained: who was right? Fat Fritz with its evaluation that ♛c4 is crushing, or Stockfish that thinks it is not bad, but not especially great either. I fed Stockfish the moves chosen by Fat Fritz to see if it could refute them, especially as the position is still very complex. 

The spectacular key move appears just three moves later after 24.f3 ♛c4 25.♕xc4 dxc4 26.♘g5 ♞d5 27.♗a5:

Don't forget you can move the pieces above!

Black's killer blow here is 27…♝a7!! With the idea of 28…♜a8. Taking the bishop leads to a quick demise after 28.♘xa7? ♜a8! 29.♘b5 ♜xa5 recovering the piece with a pawn to boot. 

Following the analysis by both engines led to many fascinating lines, but all were clearly going to win for Black. What was striking was that Stockfish was extremely slow to credit black with even a -2 advantage even 10 moves later, in spite of the extra exchange.

For example, here is a position after one line of analysis over ten moves later:

By now Fat Fritz is in the clear stratosphere judging itself at +13 or so, which just means it thinks this is a mere matter of technique. Technique it is confident it has needless to say. Here Stockfish says it plans 36.g4, expecting 36...f4 in reply, completely locking down the position, and only after two billion nodes does its evaluation begin to climb past -2 and -3 for Black. As a side note, trying to sit on the position with a move like 36.b3 fails as Black bulldozes through with 36...b5!

Clearly, this was not just a case of a missed tactic, since even after the tricky moves were past, it still struggled to perceive this as won.

Declining the exchange

Assuming there is no argument that 25.♕xc4 will lose for White, what if he declines the queen exchange with 25.♕d1!? 

Black's obvious continuation is 25...♛b4 with the nasty dual threat of ...♛xb2 and ...♛d2. What can white do? Vishy said that he had seen this line as well, but ran into a powerful resource he failed to see a way to overcome. Here he analysed — in complete agreement with Fat Fritz it should be noted — 25...♛b4 26.b3 ♛d2... 

The answer is 27.♞f2!! a superb shot that protects the queen and threatens 28.♕xd2 where the pawn will be a target. Unable to see how to continue here, this ended up being the line that prevented the former World Champion from playing it. Although there is a winning continuation here, it is hardly obvious. The continuation goes 27...♞d7 28.♗c5 ♞xc5 29.dxc5 d4!

And now the attempt to confuse the issue with 30.♕xd2 exd2 31.♘xd4 ♜d8 32.e3 fails to the elegant 32...♝e5 33.♔f1 ♝xd4 34.exd4:

And here Black wins with the simple 34...♜e8! 

Aside from the impressive evaluation by the neural network, the attractive lines punctuated by a few beautiful moves really did not deserve to be lost into oblivion — hence this article. As to Anand missing this possibility, the complexity is such that even a great player would have no reason to moan about missing it. Since he saw the power of the idea, his judgement was clearly not inferior, the problem was making the lines work.

Replay the full analysis

Conclusion

Did Fat Fritz see this all to a concrete end? Of course not. It certainly saw the mainline and the key shot 27...♝a7!! almost immediately, but further down the road it is really all about positional judgement. I think this is the sort of position that really shows just how different analysis with Fat Fritz can be, and some of the things you can expect to encounter and enjoy.

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