@9488
"The current measure for "Accuracy" is derived from human and engine play, which are both imperfect."
++ Human or engine evaluations (like +0.33) mean nothing in absolute terms.
However, each position can only be a win/draw/loss. That is the objective evaluation. It becomes apparent when the 7-men endgame table base is reached, or a prior 3-fold repetition.
Optimal play is play without errors, i.e. without moves that worsen the game state from a draw to a loss.
There have been fewer and fewer errors in the last years of ICCF correspondence play and hence fewer and fewer decisive games.
Now they are at 105 draws out of 105 games, i.e. perfect play.
@9487
"still will have only played about 1 position out of every 1,000,000,000,000,000,000,000,000,000,000 unique positions (i.e. 10^13 vs. 10^43)."
++ This mistake keeps coming up: it is not necessary to visit all legal positions to weakly solve chess as Schaeffer did for Checkers. Besides, the vast majority of the 10^44 legal positions can never result from optimal play. Look at 3 samples: https://github.com/tromp/ChessPositionRanking multiple underpromotions from both sides.
Therefore Gurion's 10^37 is a better estimate.
https://univ-avignon.hal.science/hal-03483904
Weakly solving needs only 1 black answer to the reasonable white moves, not all black moves. Hence a square root.
That leads to 10^17 positions to weakly solve Chess.
In that light 10^13 is not that far from 10^17.