Module 17: Loops
  Lecture 33: Data Dependence in Parallel Loops
 


Loop Limit Constraints

  • Loop limits add constraints
  • Lower limit is zero for normalized loop
  • Constraints are realities
  • Dependence system can be expressed in matrix notation.
A i = C
B i ≤ b
Linear equalities
Linear inequalities
(+)ve coefficient for unknown
(−)ve coefficient for unknown
Upper limit
Lower limit

Example:

for I = 2, 100
for J = 1, I-1
B[I, J] = B[J, I]
endfor
endfor

The 2 eqns. for equality are: