alt Hacker NewsDid you reach 30 by taking a number from the blog and adding to it? The first real size estimate in the post includes promoting to any piece, storing an entire 3 bits per pawn for all 16 pawns. This later gets optimized to 9 bits per side.
Did you reach 30 by taking a number from the blog and adding to it? The first real size estimate in the post includes promoting to any piece, storing an entire 3 bits per pawn for all 16 pawns. This later gets optimized to 9 bits per side.
Sorry I was in the car and read the headline and tried to see how I would do it as an exercise. I actually think I undercounted because for the king and rooks you have to store whether they have been moved yet, and for the pawns whether they just jumped two spaces (so you know if en passant is a valid move).
So I wasn't saying the article is wrong, just engaging in a bit of intellectual exercise.
My count was: there are 16 pawns, each could be in one of 64 places or not on the board, so 6+1 bits per pawn for that, and each could be promoted to a knight a bishop a rook or a queen, so 4+1 bits per pawn for that, and one of them might have just moved two spaces, so 3+1 bits for that. And the other 16 pieces don't change their nature so we only need to know where they are, so 6+1 bits for each of those, plus 3 bits for each of the rooks and the king to tell if they have already been moved. That's.. 40 bytes actually. Im really curious how they got it in 26.
Update: I see! They used illegal positions to store all the special statuses. Very clever!