Function fftn_memory_efficient 

pub fn fftn_memory_efficient<T, D>(
    x: &ArrayView<'_, T, D>,
    axes: Option<Vec<usize>>,
    _max_memory_gb: f64,
) -> FFTResult<Array<Complex64, D>>
where
    T: NumCast + Copy + Send + Sync,
    D: Dimension,

Memory-efficient FFT for very large arrays