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cannam@127:fftw_plan fftw_plan_dft_1d(int n0, cannam@127: fftw_complex *in, fftw_complex *out, cannam@127: int sign, unsigned flags); cannam@127: fftw_plan fftw_plan_dft_2d(int n0, int n1, cannam@127: fftw_complex *in, fftw_complex *out, cannam@127: int sign, unsigned flags); cannam@127: fftw_plan fftw_plan_dft_3d(int n0, int n1, int n2, cannam@127: fftw_complex *in, fftw_complex *out, cannam@127: int sign, unsigned flags); cannam@127: fftw_plan fftw_plan_dft(int rank, const int *n, cannam@127: fftw_complex *in, fftw_complex *out, cannam@127: int sign, unsigned flags); cannam@127:
Plan a complex input/output discrete Fourier transform (DFT) in zero or
cannam@127: more dimensions, returning an fftw_plan (see Using Plans).
cannam@127:
Once you have created a plan for a certain transform type and cannam@127: parameters, then creating another plan of the same type and parameters, cannam@127: but for different arrays, is fast and shares constant data with the cannam@127: first plan (if it still exists). cannam@127:
cannam@127:The planner returns NULL if the plan cannot be created. In the
cannam@127: standard FFTW distribution, the basic interface is guaranteed to return
cannam@127: a non-NULL plan. A plan may be NULL, however, if you are
cannam@127: using a customized FFTW configuration supporting a restricted set of
cannam@127: transforms.
cannam@127:
rank is the rank of the transform (it should be the size of the
cannam@127: array *n), and can be any non-negative integer. (See Complex Multi-Dimensional DFTs, for the definition of “rank”.) The
cannam@127: ‘_1d’, ‘_2d’, and ‘_3d’ planners correspond to a
cannam@127: rank of 1, 2, and 3, respectively. The rank
cannam@127: may be zero, which is equivalent to a rank-1 transform of size 1, i.e. a
cannam@127: copy of one number from input to output.
cannam@127:
cannam@127: n0, n1, n2, or n[0..rank-1] (as appropriate
cannam@127: for each routine) specify the size of the transform dimensions. They
cannam@127: can be any positive integer.
cannam@127:
cannam@127: n0 x n1; or n0 x n1 x n2; or
cannam@127: n[0] x n[1] x ... x n[rank-1].
cannam@127: See Multi-dimensional Array Format.
cannam@127: in and out point to the input and output arrays of the
cannam@127: transform, which may be the same (yielding an in-place transform).
cannam@127:
cannam@127: These arrays are overwritten during planning, unless
cannam@127: FFTW_ESTIMATE is used in the flags. (The arrays need not be
cannam@127: initialized, but they must be allocated.)
cannam@127:
cannam@127: If in == out, the transform is in-place and the input
cannam@127: array is overwritten. If in != out, the two arrays must
cannam@127: not overlap (but FFTW does not check for this condition).
cannam@127:
sign is the sign of the exponent in the formula that defines the
cannam@127: Fourier transform. It can be -1 (= FFTW_FORWARD) or
cannam@127: +1 (= FFTW_BACKWARD).
cannam@127:
cannam@127: flags is a bitwise OR (‘|’) of zero or more planner flags,
cannam@127: as defined in Planner Flags.
cannam@127:
cannam@127: FFTW computes an unnormalized transform: computing a forward followed by cannam@127: a backward transform (or vice versa) will result in the original data cannam@127: multiplied by the size of the transform (the product of the dimensions). cannam@127: cannam@127: For more information, see What FFTW Really Computes. cannam@127:
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