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--- chess:programming:bitboards [2021/10/12 13:03] – [Determine Empty Squares] peter
+++ chess:programming:bitboards [2021/10/29 00:56] (current) – peter
@@ Line 2: / Line 2: @@
 A BitBoard is comprised of a 64-bit word, which is used to store the positions of different Chess Pieces.
+<code>
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+0 0 0 0 0 0 0 0
+  a b c d e f g h
+</code>
 Every square on a Chess Board is represented by one bit in the 64-bit word.
@@ Line 160: / Line 172: @@
 ----
+===== Determine Squares which are set in both BitBoards =====
+Determine if one Bitboard is a subset of the other.
+  * Use xor (or subtraction).
+<code>
+super               sub                 super &~ sub
+. . . . . . . .     . . . . . . . .     . . . . . . . .
+. 1 1 1 1 1 1 .     . . . . . . . .     . 1 1 1 1 1 1 .
+. 1 1 1 1 1 1 .     . . 1 1 1 1 . .     . 1 . . . . 1 .
+. 1 1 1 1 1 1 .  ^  . . 1 1 1 1 . .     . 1 . . . . 1 .
+. 1 1 1 1 1 1 .     . . 1 1 1 1 . .  =  . 1 . . . . 1 .
+. 1 1 1 1 1 1 .  -  . . 1 1 1 1 . .     . 1 . . . . 1 .
+. 1 1 1 1 1 1 .     . . . . . . . .     . 1 1 1 1 1 1 .
+. . . . . . . .     . . . . . . . .     . . . . . . . .
+</code>
+----
 ===== C++ Bitwise Operators =====