Author: Russell Reagan
Date: 11:21:37 08/03/02
I have YABQ. For the longest time I didn't understand what rotated bitboards were used for, and now I understand their purpose. I'm still hung up on one thing though, and hopefully someone can explain what I'm misunderstanding. As I understand it, you use your all pieces bitboard and the rotated bitboards to compute the "state of the rank/file/diagonal", and you use that for various things, such as computing mobility, generating legal moves, or whatever. Here is my problem. Let's say that you are computing mobility for a rook, and you find that the state of the rank is 01001010, with the left bit being A1 and the right bit being H1, and the rook being on in the middle, on E1. Now, if you put this value into your mobility array, how does it know what the accurate value of mobility is here? There will be a difference in the mobility if the piece on B1 is a black piece rather than a white piece. The "state of the rank" makes no distinction between colors, so how can it accurately calculate mobility or anything else accurately from the state of the rank/file/diagonal? Another example, if the state of the rank is 11111111 with a rook on E1, the mobility could be either 0, 1, or 2, depending on the color of the pieces on D1 and F1. What am I misunderstanding? Russell
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