Basic HTML version of Foils prepared August 29 98

Foil 48 Typical Parallel Bugs (2)

From Designing and Building Parallel Programs 2: openMP Shared Memory Programming Language DoD Modernization Tutorial -- 1995-1998. by Ian Foster, Gina Goff, Ehtesham Hayder, Chuck Koelbel(Some foils prepared by Kuck & Associates, Inc.)
1 Problem: not saving values from parallel regions
  • Symptom: bad answers, core dump
  • Fix: transfer from local into shared
2 Problem: unsynchronized access
  • Symptom: bad answers
  • Fix: critical section / barrier / local accumulation
3 Problem: numerical inconsistency
  • Symptom: run-to-run variation in answers
  • Fix: different scheduling mechanisms / ordered sections / consistent parallel reductions
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