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 on whole words.

Set operation:	Bit vector operation:
∈	∧ with vector for element
	or test bit
∩	∧
∪	∨
set complement of A	¬ A
set difference, A - B	A ∧ ¬ B

Operations on the bit vector representation are O(n/32) , compared to O(n · m) with other methods.

Example: assign a bit for each program variable or subexpression.