Note that the ` RATIO` is larger than eight when ` EPS`
is larger and then decreases steadily. A small error in the code
would produce much different values.
We encourage the student to try this testing routine on several
subroutines that compute objective functions and their derivatives;
errors should be introduced into the derivative codes systematically
to examine the ability of ` TESTGH` to detect them and provide
the right diagnosis, as outlined above.