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fftw_plan fftw_plan_dft_1d(int n0, Chris@10: fftw_complex *in, fftw_complex *out, Chris@10: int sign, unsigned flags); Chris@10: fftw_plan fftw_plan_dft_2d(int n0, int n1, Chris@10: fftw_complex *in, fftw_complex *out, Chris@10: int sign, unsigned flags); Chris@10: fftw_plan fftw_plan_dft_3d(int n0, int n1, int n2, Chris@10: fftw_complex *in, fftw_complex *out, Chris@10: int sign, unsigned flags); Chris@10: fftw_plan fftw_plan_dft(int rank, const int *n, Chris@10: fftw_complex *in, fftw_complex *out, Chris@10: int sign, unsigned flags); Chris@10:Chris@10:
Chris@10: Plan a complex input/output discrete Fourier transform (DFT) in zero or
Chris@10: 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@10: parameters, then creating another plan of the same type and parameters, Chris@10: but for different arrays, is fast and shares constant data with the Chris@10: first plan (if it still exists). Chris@10: Chris@10:
The planner returns NULL if the plan cannot be created. In the
Chris@10: standard FFTW distribution, the basic interface is guaranteed to return
Chris@10: a non-NULL plan. A plan may be NULL, however, if you are
Chris@10: using a customized FFTW configuration supporting a restricted set of
Chris@10: transforms.
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rank is the rank of the transform (it should be the size of the
Chris@10: array *n), and can be any non-negative integer. (See Complex Multi-Dimensional DFTs, for the definition of “rank”.) The
Chris@10: ‘_1d’, ‘_2d’, and ‘_3d’ planners correspond to a
Chris@10: rank of 1, 2, and 3, respectively. The rank
Chris@10: may be zero, which is equivalent to a rank-1 transform of size 1, i.e. a
Chris@10: copy of one number from input to output.
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Chris@10: n0, n1, n2, or n[0..rank-1] (as appropriate
Chris@10: for each routine) specify the size of the transform dimensions. They
Chris@10: can be any positive integer.
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Chris@10: n0 x n1; or n0 x n1 x n2; or
Chris@10: n[0] x n[1] x ... x n[rank-1].
Chris@10: See Multi-dimensional Array Format.
Chris@10: in and out point to the input and output arrays of the
Chris@10: transform, which may be the same (yielding an in-place transform).
Chris@10: These arrays are overwritten during planning, unless
Chris@10: FFTW_ESTIMATE is used in the flags. (The arrays need not be
Chris@10: initialized, but they must be allocated.)
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Chris@10: If in == out, the transform is in-place and the input
Chris@10: array is overwritten. If in != out, the two arrays must
Chris@10: 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@10: Fourier transform. It can be -1 (= FFTW_FORWARD) or
Chris@10: +1 (= FFTW_BACKWARD).
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Chris@10: flags is a bitwise OR (‘|’) of zero or more planner flags,
Chris@10: as defined in Planner Flags.
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Chris@10: FFTW computes an unnormalized transform: computing a forward followed by Chris@10: a backward transform (or vice versa) will result in the original data Chris@10: multiplied by the size of the transform (the product of the dimensions). Chris@10: For more information, see What FFTW Really Computes. Chris@10: Chris@10: Chris@10: Chris@10: