Node:Real-to-Real Transforms, Next:, Previous:Real-data DFT Array Format, Up:Basic Interface

4.3.5 Real-to-Real Transforms

fftw_plan fftw_plan_r2r_1d(int n, double *in, double *out,
                           fftw_r2r_kind kind, unsigned flags);
fftw_plan fftw_plan_r2r_2d(int nx, int ny, double *in, double *out,
                           fftw_r2r_kind kindx, fftw_r2r_kind kindy,
                           unsigned flags);
fftw_plan fftw_plan_r2r_3d(int nx, int ny, int nz,
                           double *in, double *out,
                           fftw_r2r_kind kindx,
                           fftw_r2r_kind kindy,
                           fftw_r2r_kind kindz,
                           unsigned flags);
fftw_plan fftw_plan_r2r(int rank, const int *n, double *in, double *out,
                        const fftw_r2r_kind *kind, unsigned flags);

Plan a real input/output (r2r) transform of various kinds in zero or more dimensions, returning an fftw_plan (see Using Plans).

Once you have created a plan for a certain transform type and parameters, then creating another plan of the same type and parameters, but for different arrays, is fast and shares constant data with the first plan (if it still exists).

The planner returns NULL if the plan cannot be created. A non-NULL plan is always returned by the basic interface unless you are using a customized FFTW configuration supporting a restricted set of transforms, or for size-1 FFTW_REDFT00 kinds (which are not defined).