Numerical analysis of dynamical systems and the fractal dimension of boundaries. L.G.S. Duarte, L.A.C.P. da Mota, H.P. de Oliveira, R.O. Ramos, J.E.F. Skea.

PROGRAM SUMMARY
Title of program: Ndynamics
Catalogue identifier: ADKH
Ref. in CPC: 119(1999)256
Distribution format: uuencoded compressed tar file
Operating system: Linux (RedHat 5.2, Debian 2.0.34),Windows 95,98
High speed store required: 32MK words
Number of lines in distributed program, including test data, etc: 74683
Programming language used: Maple, C
Computer: Pentium II 450 PC

Nature of physical problem:
Computation and plotting of numerical solutions of dynamical systems and the determination of the fractal dimension of the boundaries.

Method of solution
The default method of integration is a 5th order Runge-Kutta scheme, but any method of integration present on the MAPLE system is available via an argument when calling the routine. A box counting method is used to calculate the fractal dimension of the boundaries.

Restrictions on the complexity of the problem
Besides the inherent restrictions of numerical integration methods, this first version of the package only deals with systems of first order differential equations.

Typical running time
This depends strongly on thE dynamical system. WIth a Pentium II 450 PC with 128 Mb of RAM, the integration of one graph (among the thousands it is necessary to calculate to determine the fractal dimension) takes from a fraction of a second to several seconds. The time for plotting the graphs depends on the number of trajectories plotted. If there are a few thousand, this may take 20 to 30 seconds.

Unusual features of the program
This package provides user-friendly software tools for analyzing the character of a dynamical system, whether it displays chaotic behaviour, etc. Options within the package allow the user to specify characteristics that separate the trajectories into families of curves. In conjunction with the facilities for altering the user's viewpoint, this provides a graphical interface for the speedy and easy identification of regions with interesting dynamics. An unusual characteristic of the package is its interface for performing the numerical integrations in C using a 5th order Runge-Kutta method. This potentially improves the speed of the numerical integration by some orders of magnitude and, in cases where it is necessary to calculate thousands of graphs in regions of difficult integration, this feature is very desirable.