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fftw_plan fftw_plan_many_dft_r2c(int rank, const int *n, int howmany, double *in, const int *inembed, int istride, int idist, fftw_complex *out, const int *onembed, int ostride, int odist, unsigned flags); fftw_plan fftw_plan_many_dft_c2r(int rank, const int *n, int howmany, fftw_complex *in, const int *inembed, int istride, int idist, double *out, const int *onembed, int ostride, int odist, unsigned flags);

Like `fftw_plan_many_dft`

, these two functions add `howmany`

,
`nembed`

, `stride`

, and `dist`

parameters to the
`fftw_plan_dft_r2c`

and `fftw_plan_dft_c2r`

functions, but
otherwise behave the same as the basic interface.

The interpretation of `howmany`

, `stride`

, and `dist`

are
the same as for `fftw_plan_many_dft`

, above. Note that the
`stride`

and `dist`

for the real array are in units of
`double`

, and for the complex array are in units of
`fftw_complex`

.

If an `nembed`

parameter is `NULL`

, it is interpreted as what
it would be in the basic interface, as described in Real-data DFT Array Format. That is, for the complex array the size is assumed to be
the same as `n`

, but with the last dimension cut roughly in half.
For the real array, the size is assumed to be `n`

if the transform
is out-of-place, or `n`

with the last dimension “padded” if the
transform is in-place.

If an `nembed`

parameter is non-`NULL`

, it is interpreted as
the physical size of the corresponding array, in row-major order, just
as for `fftw_plan_many_dft`

. In this case, each dimension of
`nembed`

should be `>=`

what it would be in the basic
interface (e.g. the halved or padded `n`

).

Arrays `n`

, `inembed`

, and `onembed`

are not used after
this function returns. You can safely free or reuse them.