Applied Parallel Computing Large Scale Scientific and Industrial Problems
Volume 1541 of the series Lecture Notes in Computer Science pp 149160
Modelica—A language for equationbased physical modeling and high performance simulation
 Peter FritzsonAffiliated withPELAB, Dept. of Computer and Information Science, Linköping University
Abstract
A new language called Modelica for hierarchical physical modeling is developed through an international effort. Modelica 1.0 [http:// www.Dynasim.se/Modelica] was announced in September 1997. It is an objectoriented language for modeling of physical systems for the purpose of efficient simulation. The language unifies and generalizes previous objectoriented modeling languages and techniques.
Compared to the widespread simulation languages available today this language offers two important advances: 1) noncausal modeling based on differential and algebraic equations; 2) multidomain modeling capability, i.e. it is possible to combine electrical, mechanical, thermodynamic, hydraulic etc. model components within the same application model.
A class in Modelica may contain variables (i.e. instances of other classes), equations and local class definitions. The multidomain capability is partly based on a notion of connectors, which are classes just like any other entity in Modelica.
Simulation models can be developed using a graphical editor for connection diagrams. Connections are established just by drawing lines between objects picked from a class library. The Modelica model is translated into a set of constants, variables and equations. Equations are sorted and converted to assignment statements when possible. Strongly connected sets of equations are solved by calling a symbolic and/or numeric solver. The C/C++ code generated from Modelica models is quite efficient.
High performance parallel simulation code can be obtained either at the coarsegrained level by identifying fairly independent submodels which are simulated in parallel, or at the finegrained level by parallelizing on clustered expression nodes in the equation graph. Preliminary results using the coarsegrained approach have been obtained in an application on simulating an autonomous aircraft watching car traffic.
 Title
 Modelica—A language for equationbased physical modeling and high performance simulation
 Book Title
 Applied Parallel Computing Large Scale Scientific and Industrial Problems
 Book Subtitle
 4th International Workshop, PARA’98 Umeå, Sweden, June 14–17, 1998 Proceedings
 Pages
 pp 149160
 Copyright
 1998
 DOI
 10.1007/BFb0095332
 Print ISBN
 9783540654148
 Online ISBN
 9783540492610
 Series Title
 Lecture Notes in Computer Science
 Series Volume
 1541
 Series ISSN
 03029743
 Publisher
 Springer Berlin Heidelberg
 Copyright Holder
 SpringerVerlag Berlin Heidelberg
 Additional Links
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 Editors
 Authors

 Peter Fritzson ^{(1)}
 Author Affiliations

 1. PELAB, Dept. of Computer and Information Science, Linköping University, S58183, Linköping, Sweden
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