slarre(3) on Linux
The text 7fcd1eac2d9a, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
the tridiagonal matrix T, SLARRE sets "small" off-diagonal elements to zero, and for each unreduced block T_i, it finds (i) the numbers sigma_i (ii) the base T_i - sigma_i I = L_i D_i L_i^T representations and (iii) eigenvalues of each L_i D_i L_i^T