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Recall that:

• There is a dependence between two iterations (I₁¹,I₂¹) and (I₁²,I₂²) if there is a memory location which is assigned to in iteration (I₁¹,I₂¹), and read in iteration (I₁²,I₂²).
  ((unless there is an intervening assignment))

• If (I₁¹,I₂¹) precedes (I₁²,I₂²) it is a data-dependence.

• If (I₁²,I₂²) precedes (I₁¹,I₂¹) it is a anti-dependence.

• If the location is assigned to in both iterations, it is an output-dependence.

• The dependence distance vector (D₁,D₂) is (I₁²-I₁¹,I₂²-I₂¹).