Basic HTML version of Foils prepared April 22 2000

Foil 27 Performance of Simplest Parallel DIT FFT III

From Parallel FFT and use in PDE Solvers Computational Science Class CPS615 -- Winter Semester 2000. by Geoffrey C. Fox
1 Tparallel (phases d-P? p< d) = N(Tcalc+Tcomm)/(Nproc) and again this is perfectly parallel (load balanced)
2 Tcomm is time to swap one complex word between 2 processors (to reduce latency this would be done as a block transfer of N/Nproc words)
3 Tcalc = T+ + T* as each processor must multiply and add/subtract. Note this implies that one loses parallelism in multiplication as both processors must do it.
4 Communication overhead fcomm = Tparallel *Nproc/Tsequential -1
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