THE SUBROUTINE fsub

This subroutine defines the function vector f t,u 6) in Eq. (B.l-la). It may be organized as in the following pseudocode. 

Subroutine fsub (t, Nstvar, U, fval, Rpar, Ipar, Irange, Imodel, Ires ) 

Double precision t, U( ), fval( ), Rpar(0 ), Integer Nstvar, lpar(0 ), Irange, Ires,. 

The argument Ires is zero on entry and should not be altered unless fsub encounters trouble, such as an illegal or undefined value of an argument or calculated quantity. To attempt recovery in DDAPLUS by taking a smaller step, return with Ires=—1. To terminate the execution, return with Ires=-2. 

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