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Finite Difference Gradients



The user is assumed to have provided analytic expressions for the values  of the nonlinear element functions in the SEIF file. The specification of analytic first derivatives is optional, but recommended whenever possible.  If the user is unable to provide analytic first derivatives of the nonlinear element functions, the derivatives will be approximated  by finite differences whenever the FINITE-DIFFERENCE-GRADIENTS keyword is specified. The user should note, however, that the accuracy of the solution obtained by LANCELOT may be compromised if finite-difference approximations are used.