Basic HTML version of Foils prepared August 7 98

Foil 12 Implementation of FORALL (cont.)

From DoD HPF Training -- 3. Parallel Constructs in HPF DoD Training and Others -- 1995-98. by Chuck Koelbel -- Rice University
Data movement becomes much more difficult on distributed memory machines if the FORALL calls a function
  • There is no race condition
  • But the data may not be on the processor where it is needed
  • And there is no synchronization point where it can be exchanged
For this reason, many implementations serialize some cases of parallel constructs
  • Usually there is a compiler override switch to parallelize at least some cases
  • Best advice: Donšt use global data in functions

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