I would not introduce yet another form of castling. How about Kevin's 'fast castling' rule?
But normally getting out 3 pieces should not be a problem. Of course it depends on whether these pieces can jump, or otherwise get out without destroying the Pawn shield. If they had to compromise the Pawn shield (e.g. like starting a Commoner on the Knight squares of the FIDE setup) that would just count as bad design. (In the Daring Dragons army of CWdA I gave the Dragoon an initial Knight jump for that reason.)
In a Grand-Chess like setup with enough empty space on the back rank there would not be a problem to clear the 2nd rank for castling; one can just retract the pieces to the back rank.
In the KingSlayer approach moving the pieces out of the castling path is encouraged, because it makes the castling right in that direction more valuable (less discounted). And the castling right with the highest weight (because it is the best of the two) would be preferred, because it contributes most to the total. So it encourages clearing one path completely before clearing the other partially (other factors such as quality of the Pawn shield being the same). This usually leads to quick clearing of one castling path. But if the other castling is still possible, it would not immediately castle, because having a second right (even when weighted less than the best right) is worth slightly more than the difference between having the right and being in the castled position. Which is what you want: keeping the opponent in the dark as long as possible so that he doesn't know what wing to aim his pieces at during development is usually a good strategy.
Of course the quality of the Pawn shield (which also takes account of enemy Pawns, such as half-open files directed at the shield, or an approaching Pawn storm) remains part of the evaluation even after castling. (But then of course only the one in the direction you actually castled.) This prevents the engine from destroying its own Pawn shield later, while it 'liberates' the Pawns on the other wing.
All this is pretty cheap, as the shield qualities are part of the Pawn-Structure evaluation, which is rarely done, because it is stored in a Pawn hash table that has a very high hit rate. The K-side and Q-side shield qualities are just two items in the Pawn hash entry. (Together with info about half-open files, passers, edge Pawns etc.) And you can stop calculating them once all castling rights are gone, which is usually pretty early in the game.
I would not introduce yet another form of castling. How about Kevin's 'fast castling' rule?
But normally getting out 3 pieces should not be a problem. Of course it depends on whether these pieces can jump, or otherwise get out without destroying the Pawn shield. If they had to compromise the Pawn shield (e.g. like starting a Commoner on the Knight squares of the FIDE setup) that would just count as bad design. (In the Daring Dragons army of CWdA I gave the Dragoon an initial Knight jump for that reason.)
In a Grand-Chess like setup with enough empty space on the back rank there would not be a problem to clear the 2nd rank for castling; one can just retract the pieces to the back rank.
In the KingSlayer approach moving the pieces out of the castling path is encouraged, because it makes the castling right in that direction more valuable (less discounted). And the castling right with the highest weight (because it is the best of the two) would be preferred, because it contributes most to the total. So it encourages clearing one path completely before clearing the other partially (other factors such as quality of the Pawn shield being the same). This usually leads to quick clearing of one castling path. But if the other castling is still possible, it would not immediately castle, because having a second right (even when weighted less than the best right) is worth slightly more than the difference between having the right and being in the castled position. Which is what you want: keeping the opponent in the dark as long as possible so that he doesn't know what wing to aim his pieces at during development is usually a good strategy.
Of course the quality of the Pawn shield (which also takes account of enemy Pawns, such as half-open files directed at the shield, or an approaching Pawn storm) remains part of the evaluation even after castling. (But then of course only the one in the direction you actually castled.) This prevents the engine from destroying its own Pawn shield later, while it 'liberates' the Pawns on the other wing.
All this is pretty cheap, as the shield qualities are part of the Pawn-Structure evaluation, which is rarely done, because it is stored in a Pawn hash table that has a very high hit rate. The K-side and Q-side shield qualities are just two items in the Pawn hash entry. (Together with info about half-open files, passers, edge Pawns etc.) And you can stop calculating them once all castling rights are gone, which is usually pretty early in the game.