The three kinds of data dependence are described in the following
way. The notation S1 , S2 , and
SN is used to denote statement 1, statement 2,
and statement N , respectively. In each example,
S2 is dependent on S1 , due to variable
X .
1. Data dependence from an assignment to a use of a variable is called flow dependence (or true dependence):
(S1): X = 3 (S2): Y = X
2. Data dependence from use of a variable to a later reassignment on that variable is called antidependence:
(S1): Y = X (S2): X = 3
3. Data dependence from an assignment of a variable to a later reassignment of that variable is called output dependence:
(S1): X = 3 : (SN): X = 4