The SIVA/DIVA package is a collection of subroutines for the solution of ordinary differential equations. There are versions for single precision and double precision arithmetic. These solutions are applicable to stiff or nonstiff differential equations of first or second order. SIVA/DIVA requires fewer evaluations of derivatives than other variable order Adams predictor-corrector methods. There is an option for the direct integration of second order equations which can make integration of trajectory problems significantly more efficient.

Other capabilities of SIVA/DIVA include:

• monitoring a user supplied function which can be separate from the derivative;
• dynamically controlling the step size;
• displaying or not displaying output at initial, final, and step size change points;
• saving the estimated local error;
• and reverse communication where subroutines return to the user for output or computation of derivatives instead of automatically performing calculations.

1. the number of equations;
2. initial values for the dependent and independent variables, integration stepsize, error tolerance, etc.; and
3. the driver program and operational parameters necessary for subroutine execution.