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A computer analysis of a game in Lichess lists your "inaccuracies", "mistakes", and "blunders". An example is below:

LiChess highlighting my "inaccuracies", "mistakes", and "blunders"

What I don't understand is why Lichess doesn't point out my good moves. It seems there is some inherent problem identifying strong moves, which is not present when pointing out poor moves.

Question: Why does Lichess only tell me my "inaccuracies", "mistakes", and "blunders", and not e.g. my "brilliancies"?

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    Define "brilliancy"? In any case, this is a purely feature related question about lichess, it makes more sense to ask it on the forum space of the said website: lichess.org/forum – user929304 May 4 at 14:56
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    See this question: Automated annotation of good moves. According to one of the answers, chesstempo has actually tried to make progress in annotating good moves, but it's not an exact science... – itub May 4 at 15:37
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    As @user929304 implies "brilliancy" is meaningless in the algorithmic world. For humans a brilliant move is one which is hard to find because we can't calculate all the possibilities but calculating all the possibilities is exactly what computers do.(within their move horizon). "Inaccuracies", "mistakes", and "blunders" are merely human terms which the programmer assigns to moves which reduce the evaluation by certain amounts. "Brilliancies" leave the evaluation unchanged as do normal moves in calm positions. – Brian Towers May 4 at 15:39
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    Well, chess.com has good move and excellent move – Marvin May 5 at 17:34
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    @Marvin i know lol, i'm agreeing with you and also saying that chess.com does even have more, with a "brilliant" move. Which implies (as you said) that it is possible, even if it isn't that easy to implement. To be fair it is a somewhat recent feature in chess.com and their analysis tool has improved quite a lot recently – Isac May 7 at 9:49
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Here's why computer analysis (on any platform) can not find brilliant moves.

They don't exist.

Now, I recognize that this seems very counter-intuitive, but bear with me. This has to do with the difference between how we (intuitively) view a chess game and how a computer (correctly) views a chess game.

When we look at a chess position, we subconsciously view the position on the board as having a certain value, and we look to improve that value.

Chess computers look at this in a completely different way.

The value that they assess the position is based on perfect play from the position forward - the only way to deviate from the perfect play is to make an error of some sort.

Example: You're losing a game by a bit, and then you find a beautiful, non-obvious tactic that nets your opponent's queen. In our human minds, we just took the game from losing to winning with our brilliancy. According to the computer, the position was already winning for you, because the computer saw the brilliancy. Any move other than the brilliancy is likely a mistake of some sort.

TL;DR

Non-obvious "brilliant" moves do not change the value of the position - they merely fulfill its potential.


Now, of course there are moves that we consider "excellent" or "brilliant" for one reason or another (requires a sacrifice, isn't immediately obvious, requires deep calculation, etc.). Don't get me wrong - it feels very rewarding to find one of these moves, and some moves are undeniably "!!" moves for human players. However, any analysis (on the part of a spectator or a player) that does not take into account the "!!" move is incorrect in the first place, and the "!!" move shows that.

Also, creating an objective definition of "brilliancy" is next to impossible - sometimes we "know" a move is brilliant, but we can't consistently explain why.

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    I think I disagree with the statement that brilliancies don't exist. By that reasoning, there are no brilliant scientists or inventors or anything else either, since the things they discover were always there for anyone to learn. – D M May 4 at 16:37
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    @DM I meant "brilliancy" as a term for chess moves only. Edited. – Brandon_J May 4 at 16:38
  • I realize you meant it that way. But I'm saying that your logic could be extended, with that result. – D M May 4 at 16:42
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    @DM ah, I see what you mean. I don't think that my logic can be extended quite so easily - a chess game is very carefully defined, with exactly one goal in mind for each side. Life is much more complicated - and still, defining "brilliancy" is going to be difficult - but I think it's a lot different from a chess move. Essentially, chess is very weakly solved by computers. Life isn't. Also, (so far) computers beat humans at chess, but not scientific discoveries. – Brandon_J May 4 at 16:47
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It's really hard to tell what a brilliancy is. For example, you might try to say that a brilliancy is a move that's much better than any other move on the board. Well, if you offer me a queen exchange and I play queen takes queen, you taking back my queen is probably a much better move than any alternative, but it's definitely not a brilliancy. So maybe a brilliancy is a non-obvious move that's much better than any alternative. OK, but what's non-obvious? Maybe you could do something based on the depth you have to go in the search tree to prove that the move is good, but that probably still isn't right because a long sequence of exchanges is usually obvious but, by construction, goes deep into the tree. Or, suppose you trap my queen: by the proof depth metric, that would be a brilliancy if I can insert a long sequence of pointless checks before you take my queen, and a normal move if I can't.

In contrast, bad moves are easy to detect: if a move is suboptimal, you just compare its score against the score of the best move and use a more negative word for bigger differences.

Fundamentally, there's only one best move in any situation. As far as the computer is concerned, you either played it or you didn't. Bad moves are bad moves, but brilliancies are good moves that most players wouldn't have seen, and that's as much a statement about "most players" as it is about "good moves".

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    Upvoted for that last sentence. Sums up the situation quite nicely. – Brandon_J May 4 at 18:42
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You are being compared to perfection

Your every move is being evaluated by a chess engine with super-human playing-strength. The default is to compare your performance to its own super-human performance. Since the engine always makes the move it itself has identified as the highest-valued, perforce it always makes the best move by definition. Hence you can only stray from this path of "perfection".

Allowing brilliance means comparing to non-perfection

To leave room for brilliant moves, or better than expected performance, it is necessary that you performance be compared to something that is not "perfect" by definition, for example the performance of a weaker engine. Theoretically, given the availability of a whole range of engine with different known ratings, each one of your moves could be categorized into a specific rating bucket.

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