Types of dependence

• If a solution to the dependence equation exists, a dependence of some kind occurs

• The dependence type depends on what solutions exist

• The solutions consist of a set of pairs (I₁,I₂)

• We would appear to have a data dependence if
  
  $${\tt A[}\phi_p(I){\tt ]} \in OUT(S_p)$$
  
  
  and
  
  $${\tt A[}\phi_q(I){\tt ]} \in IN(S_q)$$
  
  

• But we only really have a data dependence if the assignments precede the uses, ie
  • $S_p ~ \delta_< ~ S_q$ if, for each solution pair (I₁,I₂), I₁ < I₂