Bit Vector Representations
Subsets of a finite set can be efficiently represented as bit vectors, in which a given bit position is a 1 if the corresponding item is an element of the subset. Representing a 128-element set takes only 4 32-bit words of memory.
Operations on sets can be done by boolean instructions operating on whole words.
|Set operation:||Bit vector operation:|
|&isin||&and with vector for element|
|or test bit|
|set complement of A||¬ A|
|set difference, A - B||A &and ¬ B|
Operations on the bit vector representation are O(n/32) , compared to O(n · m) with other methods.
Example use: assign a bit in a bit vector for each program variable or subexpression.
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