Basic HTML version of Foils prepared 2 September 1997

Foil 14 Notes on HPF Implementation of Lapace Solver

From CPS615 Laplace Example -- Programming Models and Performance CPS615 Basic Simulation Track for Computational Science -- Fall Semester 97. by Geoffrey C. Fox
(1) DefInes a data world of NTOT entries
(2) Breaks up world into equal parts in each processor decomposed in one dimension
(3) Instructs that PHINEW AND PHIOLD are aligned exactly with world i.e. PHINEW(I) and PHIOLD(I) are stored in the I'th position of world
(4) EOSHIFT is "End-Off" SHIFT. The calls shift PHIOLD by one both to left and right. The indices take care of WORLD (1 and NTOT) being boundary values
  • EOSHIFT (and corresponding circular shift (CSHIFT) are "standard" Fortran90 array manipulation routines. They are not specific to parallel computing. We can write this statement (4) as a direct array operation.
BEGIN PHINEW(2:NTOT1) = 0.5 * (PHIOLD (1:NTOT2) + PHIOLD (3:NTOT))
(5) Forms TEST as maximum change in absolute value of j at any world location. MAXVAL is a Fortran90 intrinsic function.
NOTE: Any subscript n:m is an "array section" or set of indices

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