Basic HTML version of Foils prepared August 7 98

Foil 19 A. INDEPENDENT directives
The INDEPENDENT Directive

From DoD HPF Training -- 3. Parallel Constructs in HPF DoD Training and Others -- 1995-98. by Chuck Koelbel -- Rice University
1 Syntax:
  • !HPF$ INDEPENDENT [ , NEW( variable-list ) ]
2 Semantics:
  • INDEPENDENT is an assertion that no iteration affects any other iteration in any way
  • NEW variables are treated as if they were allocated anew for each iteration (DO only)
  • Applied to a DO: states that there are no loop carried dependences (except for NEW variables)
  • Applied to a FORALL: states that no index point assigns to any location that another uses
  • If the assertion is false, the program is not standard-conforming (i.e. results are not defined)
3 Note: INDEPENDENT is not a general parallel loop!
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