[verbify]

My father-in-law told me he watched that game live when he was a kid, and he just gasped when Fischer played Bxh2. (This is before engines or eval bars). Spassky did well to convert, but this is more about Fischer's mistake than Spassky.

This is the kind of blunder that you'd expect from a strong club player, not from Bobby Fischer. Although I understand that Fischer was brilliant but inconsistent, and to be fair, the last chess championship matches had a share of blunders.

[alex1138]

It's almost a certainty Fischer didn't just "not notice" the bishop would be trapped, he just miscalculated further down the line (in fact if you plug it into an engine, it shows an equal evaluation)

It's one of the single biggest misconceptions ever, it gets repeated endlessly

[mlyle]

> in fact if you plug it into an engine, it shows an equal evaluation

I don't think this is true, and engine evals aren't everything.

Two positions can have equal evaluations, but one can be trivial to play optimally and the other can be tricky and have a 10 move long sequence of "only moves" that are really hard to calculate. The latter is a much worse move, if you are not a chess engine.

[billforsternz]

Your last paragraph is the nicest capsule description of this very important and yet widely misunderstood computer chess concept I've seen. Thanks! I'm going to use this (probably poorly paraphrased due to my failing memory:).

[h3half]

I've often seen this described as the "sharpness" of a position

[janalsncm]

That’s reasonable, but the question we really want to know is how difficult it will be to equalize, which is a measure of both the number of equalizing moves and how difficult it is to find them. If the only moves are obvious, it’s not as bad as you might originally think.

In other words the correct calculation of subjective difficulty is a dot product, not simply a count of the number of equalizing moves.

[mlyle]

Yah, I'm not saying that a way to figure out the "difficulty of position" is to simply count the number of "only moves" or a volatility measure. There's sometimes a sequence of obvious trades to make, and that's hardly a difficult position.

It's hard to capture "obvious". One metric is how far you need to look down the eval tree to know a move is good, but even that is flawed.

[janalsncm]

Yes, it would be hard to avoid stepping into the scope of psychology to truly answer the question, because what might be easy for you might not be for me, even if we had equal elo ratings. (Trivial example, we might have equal elos but I try out a new opening you normally play.) You can probably learn a function to give a reasonable estimate though.

[mlyle]

I prefer something kind of objective rather than looking at player strengths. The "depth needed to search to pick equal move" is my best answer, maybe revised to be "and isn't found with a couple of simple heuristics" to clean it up some.

[sa46]

Is there a chess metric that combines centipawns with a complexity metric?

[fsckboy]

you are replying to a comment that says "he miscalculated an equal position further down the line" and your point of objection is that he miscalculated an equal position further down the line?

still your move

[mlyle]

You've not understood what is said.

If on move 29, you choose a move that is slightly worse but leave yourself in an extremely difficult position for you but an easy one for the other guy...

And then only on move 40 does the eval extremely diverge...

In my opinion, your real blunder was on move 29, not 40. Just because an engine could hold a position doesn't make it a reasonable move.

[fsckboy]

but that says nothing about what Fisher was thinking, so while your opinion is valid, it's not more valid than the comment you replied to, especially when your comment mimics the structure of his comment in the way I pointed out.

[mlyle]

Fisher had said that he was seeking to complicate the game-- which is something that black wants to do, in general-- add uncertainty for both sides.

In practice, the move only added uncertainty for black. White faced easy choices, and black difficult ones.

I didn't disagree that Fisher thought the move was safe and miscalculated. Indeed, he didn't even miscalculate badly-- engines think they can hold the position.

I'm asserting that the move fails because it made the subsequent game more complicated for Fisher without imposing an equal penalty on his opponent. It made a bad miscalculation almost inevitable.

[rybosworld]

> in fact if you plug it into an engine, it shows an equal evaluation

This isn't true - that move takes the game from dead equal, to +0.7 (70 centipawns favor for Boris).

It isn't a total blunder but it's objectively a poor move.

[dmurray]

A better engine or running the engine deeper will show 0.0 (or you need to show there are alternatives for White before 40... f4?!)

Though this may be a situation where the weaker engine is actually more helpful in assessing the practical situation: +0.7 is a better reflection of the relative chances in a human game than 0.0.

[verbify]

Interesting, I never knew that. Engine does give +0.6 to Spassky, so the move slightly made Fischer's position worse (https://lichess.org/study/Eyl4uwTZ/TUx5RZIk) and the engine thinks f4 (on move 40) was the blunder.

I'm not qualified to analyse this, I read into it a bit more and apparently he was trying to complicate the game, the 1973 tournament book only marks it as ?!.

[mlyle]

> the engine thinks f4 (on move 40) was the blunder.

The engine knows what move would be a blunder for computer play.

It doesn't know what move made the position impossibly tricky for a human to maintain for black.

Every game that I analyze, there's possible moves where the computer will trade endless complexity for one's side for a couple centipawn advantage. These are moves that a human should not play.

[DiogenesKynikos]

It's difficult to convey why computer evaluations are not always a good measure for whether a move made by a human is good.

I think the main point is that computers are so much better than humans at playing chess that what might be a reasonable move for them is effectively a terrible blunder for a human. It's like comparing a student driver with an F1 pro, and saying, "It's totally reasonable for the student driver to yank the wheel to the right when driving at 300 km/h, because an F1 driver would be able to recover from that." The point is that the student driver won't be able to follow up with near-superhuman ability to save the situation.

[mlyle]

Yes-- this is well put.

Of course, in this case, the engine doesn't think this is a particularly reasonable move; the evaluation just fails to show how bad it would be for a human-- even a near-superhuman chess player like prime Fischer-- to play.

[beyondCritics]

> It's one of the single biggest misconceptions ever, it gets repeated endlessly

FM Roese here (best DWZ 2399). I agree, figuring or even conjecturing that Fischer overlooked 30.g3 is totally insane. However he also did not saw the theoretical draw, this strikes me even more off. He never opened up about his idea, so in all likelihood he calculated something very stupid.

> if you plug it into an engine, it shows an equal evaluation

They criticized this argument rightly, but many basically repeated your mistake in the process of doing so. All engines use some evolved adaption of iterative refinement, be it either "Iterative deepening" (of an alpha beta search) [1] or "UCT" [2]. If you post computer evaluations you should at the very least give the reported nominal search depth and the engine name and version, otherwise you are just asking for trouble. On computer chess fora [0] they often post the whole log file bluntly.

[0] https://www.talkchess.com/

[1] https://www.chessprogramming.org/Iterative_Deepening

[2] https://www.chessprogramming.org/UCT

[bongodongobob]

Idk, I'm an amateur and that just looks like an obvious terrible move. I don't get it. What's to calculate?

[wetpaste]

I don't think it was purely a calculation error, it was probably also an intuitive evaluation. Bobby was trying to complicate the game and create an imbalance, where there were still winning chances if misplayed by spassky, but obviously it was a bad evaluation and it backfired. I think he was in a bit of a mood and got reckless. He had been making a lot of demands leading up to this and threats to not participate, probably got frustrated by the drawn endgame and took a big risk. I don't think he ever really opened up about his reasoning to be fair, but was asked along the lines of "were you trying to complicate the game" and he said "something like that". After losing those first two games he demanded the cameras to be removed from the playing hall and started to play really well against spassky, so possibly a psychological aspect from the cameras were also to blame. Maybe he knew he was throwing the game and it'd make for an entertaining match... the guy was sort of insane

[alex1138]

Well Fischer wasn't an amateur and there's no evidence he just missed a one-move refutation

[bonzini]

It still doesn't make any sense, even if he knew that the bishop was trapped. Black is the only side that can lose.

[alex1138]

Maybe, and you can argue it was a bad practical choice, but the way it usually gets DESCRIBED is basically "Fischer missed bishop get trap lol". It's really braindead