Basic HTML version of Foils prepared March 15 00

Foil 31 Red Black Parallel Gauss Seidel III

From Collection of Extra Foils for CPS615 PDE Iterative Solution Discussion CPS615 Spring Semester 00 -- March 00. by Geoffrey C. Fox


1 Do normal block decomposition
2 Parallel Phase I: Update all Red Points
  • Communicate black points at k-1 to halo in each processor
  • Compute red points to iterate k
3 Parallel Phase II: Update all Black Points
  • Communicate red points at k to halo in each processor
  • Compute black points to iterate k
4 This has similar efficiency analysis to Jacobi except a little more sensitive to latency
  • Same amount of communication but twice as many messages
5 In electrical power system and similar simulations, one gets irregular sparse matrices and no way to get such a clean parallel algorithm
  • In fact not clear if there is a sequential Gauss Seidel that converges

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