Chess will never be solved, here's why

#2762
It is all well known that the evaluation function has its flaws and fails to recognise fortresses and some other known draws. However, an early loss of a pawn means a loss of the game. The side with the extra pawn steers clear of the safe heavens.

"safe havens"

So you freely admit that engines are still flawed and cannot evaluate perfect play, yet your premise is completely reliant upon Stockfish, and you now have hitched your wagon to the idea that a +1 engine evaluation is an absolute win.  Time to resign...

Statistically, the claim that a win of a pawn wins a game is not only unsupportable, it is dubious whether the win of a pawn suffices to make the expectation of the game greater than 75% (which would be the expectation if the probability of a win was the same as the probability of a draw.

Strong evidence for this comes from Stockfish evaluations collated with results and with neural network expections.  My impression is that a 1 pawn advantage gives an expectation of about 0.7. Note that a 1 pawn advantage from Stockfish is what you have if you are 1 pawn up but it evaluates the positional factors to be balanced (positional factors adjust the material balance indicated in the evaluation).

Certainly this needs to be checked empirically in a more systematic way.

#2764
"engines are still flawed and cannot evaluate perfect play"
++ Engine evaluations are flawed especially near the end of the game,
where is does not recognise fortresses or where it does not shed material as it should to win.
That is why the calculation must go on deeply to reach the 7-men endgame table base.

"a +1 engine evaluation is an absolute win."
++ Yes, early enough +1 is a sure win as it allows to steer towards a won endgame.
Late in the endgame +1 or even +5 may not be enough if the safe haven cannot be avoided.
1 e4 b5, 1 e4 f5, 1 d4 g5 are sure wins: pawn down, no compensation.
Most gambits are losing despite the obvious but insufficient compensation.

#2766
"My impression is that a 1 pawn advantage gives an expectation of about 0.7"
Expectation is a notion of imperfect play, linked to probability of error.
A position is either a draw, a win, or a loss.
There are no intermediates.

No, not infinitely variable. That's why we have the 50 move rule.

The idea that "chess computer rated a zillion" can't analyse the Ruy Lopez better than a human is likely best left in the 20th century!

How would such a check tell you anything about perfect play?

If you try a statistical check on the result of KQKNN positions, SF14 with NNUE or human, will tell you they're generally drawn under basic rules, but Nalimov says they're 98% won by the queen.

I think all you get from looking at practical play is information about practical play.

I feel you have entirely missed a crucial fact. Suppose it is the case that a position is evaluated +1 pawns by a super-duper computer (and let's assume one side is actually a pawn up), Then suppose if you play two super-duper computers against each other in this position (or a set of such positions), the score is 70%, most of the results being draws and almost all the rest being wins for the side with the extra pawn.

You claim the mixed results are due to inaccuracy. This is correct from a game theoretic point of view if there are mixed results for a single position. But you also claim the true result is a win. This is not only unjustifiable, it is also likely to be wrong a lot of the time. If the true result was a win, why does the winning side make so many blunders to give away the draw, while the side with a pawn less makes fewer cancelling blunders? 

You can be very confident that a lot of +1.00 positions are draws. The evidence is that it is most of them, but regardless of this the notion that all of them are wins is absurd.

We don't have the 50 move rule any more under basic rules, but even when we did it wasn't compulsory to claim.

We do have a limit on games governed by competition rules since 2017. There is an automatic draw if the ply count reaches 150 or if positions with the same player to move, pieces of the same kind and colour occupying the same squares and the possible moves of all the pieces of both players the same occur five times. 

Evidence?

First, I acknowledge that the actual results of games between imperfect players from positions don't tell you what the tablebase value is. But I conjecture that for a lot of the sort of positions where chess experience is most relevant, they are likely to be some sort of indication. People lose dead lost openings a lot. Top evenly matched players probably draw theoretically drawn positions a lot. Not proof, but seems most likely (like the opening position being a draw is a reasonable conjecture based on white's 54% score in master play (or whatever it is).

Leela has learnt to estimate the expected result in positions reached in games and an informal observation is that a pawn according to Stockfish is somewhere around a 70% expectation.

A random example is not so far from that:

[This post replied to a now deleted post]

I am not and I acknowledge that you are right to question this. It's based on a loose notion of randomness of the errors producing results. This notion can be quantified.

To a tablebase you can think of there only being 3 classes of error, all of which change the value. There are of course no errors for a losing player, one class of error for a player in a drawing position, and two classes of errors for a player in a winning position.  With some reasonable assumptions about the statistics of these errors, you will find it implausible that a class of losing positions usually end up as draws. (The statistics needed to achieve this would be that errors turning a win into a draw are much more common than those turning a draw into a loss. If the frequencies of different types of errors are comparable, you would find that if you have enough errors to turn most losses into draws, you would have quite a few wins for the other side too). Of course, this also provides a loose argument that the large number of draws in top level games does indeed mean the value of chess is a draw. Elsewhere you will find me pointing out that this argument leaves uncertainty so doesn't tell us the value for sure. I am acknowledging this uncertainty here as well.

How could Stockfish assign an advantage of +9 there?
Chess diagrams don't copy - but in the quoted post the White king simply keeps black's King immobile - which paralyzes black's material advantage of two rooks and a bishop. 

The strongest engines are stronger than top GM's these days.
But for solving projects and chess research would engines be used that make that kind of mistake of failing to factor position versus material ?

If engines are still that Primitive (hard to believe) - and that persists - then Indeed chess will never be solved on this planet.
If aliens come from this galaxy or from another (or from another Big bang) who have a 'solution' ...  then programmers' reaction to the aliens' algorithm:  could be what?
What could they offer the alien?
Alien:  "Don't worry.  You've got more troubles with global warmings and too many nukes and other problems.  If we offered you the chess algorithms - that's not going to motivate you to do anything about those other things."

So - another thing coming out of the discussion -
that Stockfish could be So Inaccurate ...
@Elroch 's contribution to be added to that of @MARattigan 's about the analysis button indicating a win where white can draw.

The reason Stockfish is not good at evaluating anomalous positions like that is that no-one has prioritised it in Stockfish development. Playing better in any position that could arise in a game without the result being clear is worth investing time in for the main purpose of being a strong player.

Regarding probabilistic evaluation and the exciting feature of Leela that probabilities of all 3 results can be predicted (and how that changes the view of a game as it progresses), here is a very interesting blog post:

https://lczero.org/blog/2020/04/wdl-head/

I clicked on that.  Read some of it.
'Probability' versus material imbalance ...
I would say todays chess computers do factor in some position into their evals.
The idea of advantage of +1 corresponding to one pawn up or material equivalent is basically flawed right away?  Probably. 
but its apparently factored in because people 'can relate to that.'

Noting in the article that AlphaZero used 'probability'.
There was quite a stir when AlphaZero first came out.

I think people can relate to odds and probability -
but many chessplayers may not like that though.
And many players prefer to see chess as removed from luck and money odds.
But for chess research projects - why not use probability?
In the current eval schemes - like on Stockfish -
what would be the difference between +30 and +50?

The reason evaluations on traditional engines are in centipawns is because they started with the standard piece values then added on a load of fudge factors for positional factors. It's a horrible mess because it is possible and there was no obvious alternative that was practical.

The reason evaluations on neural networks are in probabilities is because the rules of chess say the aim is to win and that a draw is of intermediate value (usually half a win).  It's just the obvious way to do it, and closely related to what is done in the most common and best developed branches of machine learning.

When AlphaZero first came out - it crushed !
Apparently not only building on probability instead of material values but also organizing its calculations better.
That's one of the marks of a better player.
Which calculations to do early. 
To do that right - observation needs to be distinguished from calculation.

Looks like a postaround there.
That's one of the good things about @tygxc - and the people responding to him or otherwise posting - they are neither deterred nor baited.