Basic HTML version of Foils prepared 26 September 1996

Foil 109 Vector Indices in FORALL's

From HPCC Software Technologies Fall 96 -- Overview and HPF Delivered Lectures of CPS615 Basic Simulation Track for Computational Science -- 26 September 96. by Geoffrey C. Fox
Consider FORALL( i=1:n ) a(ix(i)) = a(i)
is allowed in HPF but will only give sensible reproducible results if ix(i) is a true permutation of 1...n
  • but if ix(i) has repeated values, then the result is undefined
Of course we always use "old" value" of a(i) on rhs so that if ix(i)= i+1 and a(0) defined, then result is
  • a(i)/new = a(i-1)/old
  • and not result of recursion
  • a(1)/new =a(0)/old
  • a(2)/new = a(1)/new just calculated = a(0)/old

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