FFTW 3.3.8: Guru Real-data DFTs

Chris@82:

fftw_plan fftw_plan_guru_dft_r2c(
Chris@82:      int rank, const fftw_iodim *dims,
Chris@82:      int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82:      double *in, fftw_complex *out,
Chris@82:      unsigned flags);
Chris@82: 
Chris@82: fftw_plan fftw_plan_guru_split_dft_r2c(
Chris@82:      int rank, const fftw_iodim *dims,
Chris@82:      int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82:      double *in, double *ro, double *io,
Chris@82:      unsigned flags);
Chris@82: 
Chris@82: fftw_plan fftw_plan_guru_dft_c2r(
Chris@82:      int rank, const fftw_iodim *dims,
Chris@82:      int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82:      fftw_complex *in, double *out,
Chris@82:      unsigned flags);
Chris@82: 
Chris@82: fftw_plan fftw_plan_guru_split_dft_c2r(
Chris@82:      int rank, const fftw_iodim *dims,
Chris@82:      int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82:      double *ri, double *ii, double *out,
Chris@82:      unsigned flags);
Chris@82:

Plan a real-input (r2c) or real-output (c2r), multi-dimensional DFT with Chris@82: transform dimensions given by (rank, dims) over a Chris@82: multi-dimensional vector (loop) of dimensions (howmany_rank, Chris@82: howmany_dims). dims and howmany_dims should point Chris@82: to fftw_iodim arrays of length rank and Chris@82: howmany_rank, respectively. As for the basic and advanced Chris@82: interfaces, an r2c transform is FFTW_FORWARD and a c2r transform Chris@82: is FFTW_BACKWARD. Chris@82:

The last dimension of dims is interpreted specially: Chris@82: that dimension of the real array has size dims[rank-1].n, but Chris@82: that dimension of the complex array has size dims[rank-1].n/2+1 Chris@82: (division rounded down). The strides, on the other hand, are taken to Chris@82: be exactly as specified. It is up to the user to specify the strides Chris@82: appropriately for the peculiar dimensions of the data, and we do not Chris@82: guarantee that the planner will succeed (return non-NULL) for Chris@82: any dimensions other than those described in Real-data DFT Array Format and generalized in Advanced Real-data DFTs. (That is, Chris@82: for an in-place transform, each individual dimension should be able to Chris@82: operate in place.) Chris@82: Chris@82:

in and out point to the input and output arrays for r2c Chris@82: and c2r transforms, respectively. For split arrays, ri and Chris@82: ii point to the real and imaginary input arrays for a c2r Chris@82: transform, and ro and io point to the real and imaginary Chris@82: output arrays for an r2c transform. in and ro or Chris@82: ri and out may be the same, indicating an in-place Chris@82: transform. (In-place transforms where in and io or Chris@82: ii and out are the same are not currently supported.) Chris@82:

flags is a bitwise OR (‘|’) of zero or more planner flags, Chris@82: as defined in Planner Flags. Chris@82:

In-place transforms of rank greater than 1 are currently only Chris@82: supported for interleaved arrays. For split arrays, the planner will Chris@82: return NULL. Chris@82: Chris@82:

4.5.4 Guru Real-data DFTs