Basic HTML version of Foils prepared 2 September 1997

Foil 25 Implementation of GLOBALMAX (TEST)

From CPS615 Laplace Example -- Programming Models and Performance CPS615 Basic Simulation Track for Computational Science -- Fall Semester 97. by Geoffrey C. Fox
1 In MPI, this is a single call
2 CALL MPI_ALLREDUCE (TEST,TEST,1,MPI_REAL,MPI_MAX,comm)
3 Flag MPI_MAX specifies global maximum
4 The implementation is quite subtle and usually involves a logarithmic tree
5 There is a clever extension to get maximum in all processors in "same" time as that on one processor on hypercube and other architectures
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© on Tue Oct 7 1997