Author: Ed Trice
Date: 19:08:11 01/14/04
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Hello Federico, >Hi to all > >In my engine I use some bitboards, but nothing about rotated bitboards for >bishop, rooks and queen moves. > >What chess sources or web pages can you recommend me? > >One answer can be Crafty. Seems to be a little difficult to understand but I >don't tried yet :-) > I definitely recommend reading the Crafty code for rotated bitboards. Basically, you create rotated versions of the board so the shifting left and right "behave" like diagonal displacements. For example, shifting bits from left to right in increments of 1 would be like moving a rook horiztonally. But, if you lay the board out like this (a 45 degree rotation) a1, b1,a2, c1,b2,a3, d1,c2,b3,a4, e1,d2,c3,b4,a5, .... you can perform shifts on the BITS corresponding to these squares as if you were actually doing complex digaonl shifts. The hard part for will be keeping track of the length of the diagonals for all of the rotation possibilies (rotating right 45, rotating left 45, etc.) as well as all of the rotation data. --Ed
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