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fftw_plan fftw_plan_guru_dft( Chris@10: int rank, const fftw_iodim *dims, Chris@10: int howmany_rank, const fftw_iodim *howmany_dims, Chris@10: fftw_complex *in, fftw_complex *out, Chris@10: int sign, unsigned flags); Chris@10: Chris@10: fftw_plan fftw_plan_guru_split_dft( Chris@10: int rank, const fftw_iodim *dims, Chris@10: int howmany_rank, const fftw_iodim *howmany_dims, Chris@10: double *ri, double *ii, double *ro, double *io, Chris@10: unsigned flags); Chris@10:Chris@10:
Chris@10: These two functions plan a complex-data, multi-dimensional DFT
Chris@10: for the interleaved and split format, respectively.
Chris@10: Transform dimensions are given by (rank, dims) over a
Chris@10: multi-dimensional vector (loop) of dimensions (howmany_rank,
Chris@10: howmany_dims). dims and howmany_dims should point
Chris@10: to fftw_iodim arrays of length rank and
Chris@10: howmany_rank, respectively.
Chris@10:
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flags is a bitwise OR (‘|’) of zero or more planner flags,
Chris@10: as defined in Planner Flags.
Chris@10:
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In the fftw_plan_guru_dft function, the pointers in and
Chris@10: out point to the interleaved input and output arrays,
Chris@10: respectively. The sign can be either -1 (=
Chris@10: FFTW_FORWARD) or +1 (= FFTW_BACKWARD). If the
Chris@10: pointers are equal, the transform is in-place.
Chris@10:
Chris@10:
In the fftw_plan_guru_split_dft function,
Chris@10: ri and ii point to the real and imaginary input arrays,
Chris@10: and ro and io point to the real and imaginary output
Chris@10: arrays. The input and output pointers may be the same, indicating an
Chris@10: in-place transform. For example, for fftw_complex pointers
Chris@10: in and out, the corresponding parameters are:
Chris@10:
Chris@10:
ri = (double *) in; Chris@10: ii = (double *) in + 1; Chris@10: ro = (double *) out; Chris@10: io = (double *) out + 1; Chris@10:Chris@10:
Because fftw_plan_guru_split_dft accepts split arrays, strides
Chris@10: are expressed in units of double. For a contiguous
Chris@10: fftw_complex array, the overall stride of the transform should
Chris@10: be 2, the distance between consecutive real parts or between
Chris@10: consecutive imaginary parts; see Guru vector and transform sizes. Note that the dimension strides are applied equally to the
Chris@10: real and imaginary parts; real and imaginary arrays with different
Chris@10: strides are not supported.
Chris@10:
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There is no sign parameter in fftw_plan_guru_split_dft.
Chris@10: This function always plans for an FFTW_FORWARD transform. To
Chris@10: plan for an FFTW_BACKWARD transform, you can exploit the
Chris@10: identity that the backwards DFT is equal to the forwards DFT with the
Chris@10: real and imaginary parts swapped. For example, in the case of the
Chris@10: fftw_complex arrays above, the FFTW_BACKWARD transform
Chris@10: is computed by the parameters:
Chris@10:
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ri = (double *) in + 1; Chris@10: ii = (double *) in; Chris@10: ro = (double *) out + 1; Chris@10: io = (double *) out; Chris@10:Chris@10: Chris@10: Chris@10: