Function eigh_with_options 

pub fn eigh_with_options<O>(
    operator: &O,
    options: EighOptions,
) -> Result<Eigensystem>
where
    O: LinearOperator + ?Sized,

Compute the complete Hermitian spectrum with optional vector elision.

The operator is materialized once as dense storage. This routine is for finite systems where the cubic full-spectrum cost is intentional.