pub unsafe extern "C" fn fftw_plan_many_r2r(
rank: c_int,
n: *const c_int,
howmany: c_int,
in_: *mut f64,
inembed: *const c_int,
istride: c_int,
idist: c_int,
out: *mut f64,
onembed: *const c_int,
ostride: c_int,
odist: c_int,
kind: *const fftw_r2r_kind,
flags: c_uint,
) -> fftw_plan