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fftw_plan fftw_plan_dft_1d(int n0, Chris@19: fftw_complex *in, fftw_complex *out, Chris@19: int sign, unsigned flags); Chris@19: fftw_plan fftw_plan_dft_2d(int n0, int n1, Chris@19: fftw_complex *in, fftw_complex *out, Chris@19: int sign, unsigned flags); Chris@19: fftw_plan fftw_plan_dft_3d(int n0, int n1, int n2, Chris@19: fftw_complex *in, fftw_complex *out, Chris@19: int sign, unsigned flags); Chris@19: fftw_plan fftw_plan_dft(int rank, const int *n, Chris@19: fftw_complex *in, fftw_complex *out, Chris@19: int sign, unsigned flags); Chris@19:Chris@19:
Chris@19: Plan a complex input/output discrete Fourier transform (DFT) in zero or
Chris@19: more dimensions, returning an fftw_plan (see Using Plans).
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Once you have created a plan for a certain transform type and Chris@19: parameters, then creating another plan of the same type and parameters, Chris@19: but for different arrays, is fast and shares constant data with the Chris@19: first plan (if it still exists). Chris@19: Chris@19:
The planner returns NULL if the plan cannot be created. In the
Chris@19: standard FFTW distribution, the basic interface is guaranteed to return
Chris@19: a non-NULL plan. A plan may be NULL, however, if you are
Chris@19: using a customized FFTW configuration supporting a restricted set of
Chris@19: transforms.
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rank is the rank of the transform (it should be the size of the
Chris@19: array *n), and can be any non-negative integer. (See Complex Multi-Dimensional DFTs, for the definition of “rank”.) The
Chris@19: ‘_1d’, ‘_2d’, and ‘_3d’ planners correspond to a
Chris@19: rank of 1, 2, and 3, respectively. The rank
Chris@19: may be zero, which is equivalent to a rank-1 transform of size 1, i.e. a
Chris@19: copy of one number from input to output.
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Chris@19: n0, n1, n2, or n[0..rank-1] (as appropriate
Chris@19: for each routine) specify the size of the transform dimensions. They
Chris@19: can be any positive integer.
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Chris@19: n0 x n1; or n0 x n1 x n2; or
Chris@19: n[0] x n[1] x ... x n[rank-1].
Chris@19: See Multi-dimensional Array Format.
Chris@19: in and out point to the input and output arrays of the
Chris@19: transform, which may be the same (yielding an in-place transform).
Chris@19: These arrays are overwritten during planning, unless
Chris@19: FFTW_ESTIMATE is used in the flags. (The arrays need not be
Chris@19: initialized, but they must be allocated.)
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Chris@19: If in == out, the transform is in-place and the input
Chris@19: array is overwritten. If in != out, the two arrays must
Chris@19: not overlap (but FFTW does not check for this condition).
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sign is the sign of the exponent in the formula that defines the
Chris@19: Fourier transform. It can be -1 (= FFTW_FORWARD) or
Chris@19: +1 (= FFTW_BACKWARD).
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Chris@19: flags is a bitwise OR (‘|’) of zero or more planner flags,
Chris@19: as defined in Planner Flags.
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Chris@19: FFTW computes an unnormalized transform: computing a forward followed by Chris@19: a backward transform (or vice versa) will result in the original data Chris@19: multiplied by the size of the transform (the product of the dimensions). Chris@19: For more information, see What FFTW Really Computes. Chris@19: Chris@19: Chris@19: Chris@19: