Function chegvd_buffer_size 

pub fn chegvd_buffer_size(
    ctx: &Context,
    eig_type: EigenType,
    mode: EigenMode,
    fill_mode: FillMode,
    n: usize,
    a: &DeviceMemory<Complex32>,
    lda: usize,
    b: &DeviceMemory<Complex32>,
    ldb: usize,
    w: &DeviceMemory<f32>,
) -> Result<usize>