Basic HTML version of Foils prepared August 7 98

Foil 18 Gaussian Elimination: Mapping

From DoD HPF Training -- 5. Parallel Programming in HPF DoD Training and Others -- 1995-98. by Chuck Koelbel -- Rice University
This program is harder for the compiler.
  • Allocate portion of array on each processor based on DISTRIBUTE
  • Apply owner-computes rule analytically based on left-hand side
  • Detect communication from dependence analysis & intrinsics
  • Here, it really pays to transform the program!
    • Reorder computation to always precompute the next pivot column
    • Rearrange communication to pipeline the series of updates
    • Do broadcasts asynchronously
    • Net result: 2¥ speedup
  • Use standard numbering for processors

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