How much is castling worth?

[chrisw]

Yeah, something was buggy, very sorry @hgm , previous results are crap.

Here the good ones :

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
White vs Black: 93 - 50 - 457 [0.536] 600 => 53% white win rate

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQ - 0 1
White vs Black: 49 - 3 - 48 [0.730] 100 => 73% white win rate

rnbqkbnr/ppppp1pp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
White vs Black: 78 - 3 - 19 [0.875] 100 => 87% white win rate

Looks like castling rights is a bit less than f7 pawn odd.

Loss of castling rights will be highly dependent on whether or not the opponent knows it.

[hgm]

Well, in chess the players are supposed to know all aspects of the game state.

Based on the percentages castling rights would be worth about 60cP. If we equate Pawn odds to 100cP. The results are rather extreme, and might be outside the linear range, though. It might be interesting to play the handicaps directly against each other, e.g. delete white's f2 Pawn, and black's castling rights.

A score of +400 for the Pawn-odds start position seems excessive. I am pretty sure that deleting f7 can be more than compensated by deleting white's Knight on b1. The Knight odds in itself would not score over 325cP, would it?

[xr_a_y]

Here are Minic results for missing f7 pawn and missing b1 knight rnbqkbnr/ppppp1pp/8/8/8/8/PPPPPPPP/R1BQKBNR w KQkq - 0 1
(still using a little random blur for the first few moves)

Code: Select all

White vs Black: 4 - 91 - 5  [0.065] 100     => 6% white win rate

Note that Minic evaluates

rnbqkbnr/ppppp1pp/8/8/8/8/PPPPPPPP/R1BQKBNR w KQkq - 0 1 => -500

and

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/R1BQKBNR w KQkq - 0 1 => -430

[hgm]

It thinks it is better for black if he doesn't have the f-pawn??? And deleting the knight drops the score 900cP (from +400 to -500) in that case?

This is why I think engine evaluations of opening positions are mostly meaningless. What does make sense is that the f-pawn is not nearly worth as much as a knight.