Basic HTML version of Foils prepared April 22 2000

Foil 30 What's Going On with DIT/DIF IV

From Parallel FFT and use in PDE Solvers Computational Science Class CPS615 -- Winter Semester 2000. by Geoffrey C. Fox
1 For DIF, the phases are of course reversed in the way the step through the binary digits of f(m) and GN(k,f)
2 One still has d phases labeled by p
3 At first recursion p=0 one is manipulating f(m) with highest binary index md-1 and forming GN(k,f) with binary index k0
4 The first DIF computations are done at end of recursion and this is "natural" m=0 and kd-1 index for GN(k,f)
5 DIF has an identical parallel performance to DIT although some of the steps differ in detail
in Table To:

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