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2.4.1 Derivative Programming     continued...

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.

(See exercises 6 and 6.)