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#### 4.4.3 Advanced Real-to-real Transforms

         fftw_plan fftw_plan_many_r2r(int rank, const int *n, int howmany,
                                      double *in, const int *inembed,
                                      int istride, int idist,
                                      double *out, const int *onembed,
                                      int ostride, int odist,
                                      const fftw_r2r_kind *kind, unsigned flags);

Like `fftw_plan_many_dft`, this functions adds `howmany`, `nembed`, `stride`, and `dist` parameters to the `fftw_plan_r2r` function, but otherwise behave the same as the basic interface. The interpretation of those additional parameters are the same as for `fftw_plan_many_dft`. (Of course, the `stride` and `dist` parameters are now in units of `double`, not `fftw_complex`.)

Arrays `n`, `inembed`, `onembed`, and `kind` are not used after this function returns. You can safely free or reuse them.