Basic HTML version of Foils prepared April 22 2000

Foil 5 Solving Poisson's Equation with the FFT II

From Parallel FFT and use in PDE Solvers Computational Science Class CPS615 -- Winter Semester 2000. by Geoffrey C. Fox


So solution of Poisson's equation involves the following steps
1) Find the Fourier coefficients fjk of f(x,y) by performing integral
2) Form the Fourier coefficients of ? by ?jk = fjk / (-p2j2 - p2k2)
3) Construct the solution by performing sum ?(x,y)
There is another version of this (Discrete Fourier Transform) which deals with functions defined at grid points and not directly the continuous integral
  • Also the simplest (mathematically) transform uses exp(-2pijx) not sin(p jx)
  • Let us first consider 1D discrete version of this case
  • PDE case normally deals with discretized functions as these needed for other parts of problem



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