Function eigsh_with_initial 

pub fn eigsh_with_initial<O>(
    operator: &O,
    options: EigshOptions,
    initial: &[Complex64],
) -> Result<Eigensystem>
where
    O: LinearOperator + ?Sized,

Compute selected eigenpairs from one explicit initial vector.

The vector must match the square operator dimension and have nonzero finite norm. Small problems may still choose the exact dense route.