I need to calculate the eigenvector from the highest eigenvalue of an ill-conditioned matrix (kappa > 10^15). Since my goal is not to search for maxima/minima nor to calculate all eigenvectors, I'm not sure whether the ill-condition may be an issue.
Hi, a numerical solution would be to perform the same calculations with a higher precision arithmetic. In FORTRAN for exemple you can switch from DOUBLE PRECISION to REAL*16. The same thing can be possible with other languages. Also with MAPLE or MATHEMATICA it is perhaps possible to obtain the "exact" solution.
I feel you try to compute maximum eigen value and corresponding eigen vector by Power's method. Since the smallest eigen value will be near zero, it will not create any problem in convergence of the procedure.