JAC

Used to indicate whether derivatives are supplied by the user or to be obtained by differencing :

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JAC=0 : No derivatives are given by the user. (Most demos use JAC=0.)

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JAC=1 : Derivatives with respect to state- and problem-parameters are given in the user-supplied routines FUNC, BCND, ICND and FOPT, where applicable. This may be necessary for sensitive problems. It is also recommended for computations in which AUTO generates an extended system, for example, when ISW=2. (For ISW see Section 10.8.3.)
(Demos int, dd2, obt, plp, ops.)