This paper describes extensions of and improvements to an efficient numerical integration method, the Implicit Modeling Package (IMP), which was presented in the July 1974 issue of SIMULATION and subsequent ly in the July 1979 issue of SIMULATION. The exten sion described here is a simulation language, General Equation Modeling System (GEMS), for the solution of systems of algebraic and differential equations. GEMS provides a simple and convenient way to formulate complex mathematical models for simulation using the IMP algorithms. GEMS is well suited for the solution of sets of stiff, nonlinear algebraic and differential equations. The GEMS package is compared to ACSL (Advanced Continuous Simulation Language) using a set of nine benchmark problems.
Presently he is a member of the board of directors of Control Data Corporation. He has more than 80 publications to his credit, including books on transfer operations, thermodynamics, kinetics, process dynamics and control, software simulation packages, and nonlinear optimization. ABSTRACT THis paper describes and illustrates extensions and iimprovements to a particularly efficient numerical integration method which was first presented in the July 1974 issue of Simulation.5 The algorithm is a single-step A-stabZe implicit method. The recent improvements provide better control over error in both integration and roundoff and greater computational efficiency than current methods for both linear and nonlinear systems. The results of applying the new algorithm to seven benchmark problems are reported and are compared with results obtained in solving the same problems by Gear's method.
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