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4.3.1 Complex DFTs

     fftw_plan fftw_plan_dft_1d(int n0,
                                fftw_complex *in, fftw_complex *out,
                                int sign, unsigned flags);
     fftw_plan fftw_plan_dft_2d(int n0, int n1,
                                fftw_complex *in, fftw_complex *out,
                                int sign, unsigned flags);
     fftw_plan fftw_plan_dft_3d(int n0, int n1, int n2,
                                fftw_complex *in, fftw_complex *out,
                                int sign, unsigned flags);
     fftw_plan fftw_plan_dft(int rank, const int *n,
                             fftw_complex *in, fftw_complex *out,
                             int sign, unsigned flags);

Plan a complex input/output discrete Fourier transform (DFT) in zero or more dimensions, returning an fftw_plan (see Using Plans).

Once you have created a plan for a certain transform type and parameters, then creating another plan of the same type and parameters, but for different arrays, is fast and shares constant data with the first plan (if it still exists).

The planner returns NULL if the plan cannot be created. In the standard FFTW distribution, the basic interface is guaranteed to return a non-NULL plan. A plan may be NULL, however, if you are using a customized FFTW configuration supporting a restricted set of transforms.

Arguments

FFTW computes an unnormalized transform: computing a forward followed by a backward transform (or vice versa) will result in the original data multiplied by the size of the transform (the product of the dimensions). For more information, see What FFTW Really Computes.