Basic HTML version of Foils prepared February 13 00

Foil 12 Sequential Programming with Guard Rings

From Master Set for Parallel Programming for Laplace's Equation CPS615 Spring Semester 00 -- February 00. by Geoffrey C. Fox


1 The concept of guard rings/points/"halos" is well known in sequential case where one has for a trivial example in one dimension (shown above) 16 points.
2 The end points are fixed boundary values
3 One could save space and dimension PHI(14) and use boundary values by statements for I=1,14 like
  • IF( I.EQ.1) Valueonleft = BOUNDARYLEFT
  • ELSE Valueonleft = PHI(I-1) etc.
4 But this is slower and clumsy to program due to conditionals INSIDE Loop and one dimensions instead PHI(16) storing boundary values in PHI(1) and PHI(16)
  • Updates are performed as DO I =2,15
  • and without any test Valueonleft = PHI(I-1)

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