This example finds the Schur factorization of the matrix such that the real positive eigenvalues of $A$ are the top left diagonal elements of the Schur form, $T$. Estimates of the condition numbers for the selected eigenvalue cluster and corresponding invariant subspace are also returned.

Note that the block size (NB) of $64$ assumed in this example is not realistic for such a small problem, but should be suitable for large problems.