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[Licence| Download | New Version Template] adzf_v3_0.tar.gz(20 Kbytes)
Manuscript Title: Finding higher order Darboux polynomails for a family of rational first order ordinary differential equations
Authors: J. Avellar, A.L.G.C. Claudino, L.G.S. Duarte, L.A.C.P. da Mota
Program title: Lsolver
Catalogue identifier: ADZF_v3_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 195(2015)216
Programming language: Maple, release 17.
Computer: Any computer running Maple.
Operating system: Windows XP, Windows 7.
RAM: 20 Mb
Keywords: Symbolic Computation, Dynamical systems, Integrating factors, Integrability.
PACS: 02.30.Hq.
Classification: 4.3.

Does the new version supersede the previous version?: Yes

Nature of problem:
We deal with the analytical solving of 1ODEs via a Darboux method.

Solution method:
The method of solution is based on the standard Prelle-Singer (Darboux) method [1], with extensions of our own [2] which solves 1ODEs with Liouvillian solutions. The first part of the Method depends on the finding of the Darboux polynomials for the ODE. The integrability analysis mentioned above is performed at this stage.

Reasons for new version:
A great portion of our work has been concentrated on analyzing and solving systems of first and second order differential equations (1ODEs and 2ODEs, respectively) from a numerical point of view [3], using Lie methods [4, 5] and Darboux type approaches [2, 6]. The common factor among the algorithms in the Darbouxian approach has always been that the most costly step is the determination of the associated Darboux polynomials. So, we are hereby trying to improve on this aspect.

Summary of revisions:
The revision is the introduction of an option to the command Darboux that allows for faster finding of the necessary Darboux polynomials and co-factors, in some cases. In the last version of this package, we have introduced a possibility of using a defined degree for both the Darboux polynomial and co-factor. Previously, one could only change the degree of the Darboux polynomial and the program used the maximum value possible for the degree of the co-factor. It causes the program to be stuck (sometimes) in a very large problem and the package had problems both in time and computer memory management. Here we introduce a similar idea. We allow the program to look for Darboux polynomials with a fixed degree in one variable. We also fix the degree of the polynomial as a whole. This extra liberty (in restricting the problem to be dealt with) allows for the success of the package in solving some 1ODEs that were missed even with the improvement of the last version. In other words, by fixing the degree for the specific variable we divided the search into smaller steps, dividing the problem into smaller ones. This prevents the algorithm entering too large a calculation.
In order to properly see the syntax of the usage of the command, please, see the example Maple file.
Let us just display the general format of the command Darboux.

> Darboux(ode,DPEXT=[[dx,dt],[x,y]])

This would produce an output of the form:

[[Darboux polynomials],[co-factors]]

In the above calling of the command Darboux, the [dx,dt] terms refer to the degrees of x and the total degree of the Darboux polynomial, respectively.
It is important to notice that, for some cases, if we do not instruct the Darboux command which degree to use for the variable x (for example) and the total degree of the Darboux polynomial, thus going step-by-step on the algorithm, (via the extra term DPEXT = [[dx,dt],[x, y]), the command may not be able to solve the 1ODE. Furthermore, the Maple in-built dsolve command can not solve some of the same class of 1ODEs. So the new improvement, albeit simple to implement, is of great practical value.

Restrictions:
The finding of the Darboux polynomials and the correspondent co-factors is the most time-demanding task of the method. So, one could say that, for the general case, if the degree for the Darboux polynomials is "4", for instance, it would make the case hard to deal with. This situation is mitigated (for some 1ODEs) by the improvements hereby introduced.

Unusual features:
The faster way to find high (>3) degree Darboux polynomials and co-factors for some cases.

Running time:
This depends strongly on the 1ODE being analyzed. As mentioned above, a degree for the Darboux polynomials "4" or above could (in general) make dealing with the case unpractical. For the degree "3", the routines may take more than a minute to deal with the task. Generally, the program takes, at most, for the other cases, a few seconds. Now, even for degrees >4 it can sometime only take a couple of seconds.

References:
[1] M. Prelle, M. Singer, Trans. Amer. Math. Soc. 279 (1983) 215.
[2] L.G.S. Duarte and L.A.C.P. da Mota, Finding Elementary First Integrals for Rational Second Order Ordinary Differential Equations, Journal of Mathematical Physics, Volume 50, Issue 1, pp. 013514-013514-17 (2009)
[3] L.G.S. Duarte, L.A.C.P. da Mota , H.P. de Oliveira, R.O. Ramos and J.E.F. Skea, Numerical Analysis of Dynamic Systems and the Fractal Dimension of Boundaries, Computer Physics Communications, 119/2-3, 256-271, (1999).
[4] E.S. Cheb-Terrab, L.G.S. Duarte and L.A.C.P. da Mota, Computer Algebra Solving of First Order ODEs Using Symmetry Methods. Comput.Phys.Commun., 101, 254, (1997).
[5] E.S. Cheb-Terrab, L.G.S. Duarte and L.A.C.P. da Mota, Computer Algebra Solving of Second Order ODEs Using Symmetry Methods. Comput.Phys.Commun., 108, 90, (1998).
[6] L.G.S. Duarte, S.E.S.Duarte, L.A.C.P. da Mota and J.F.E. Skea, Solving second order ordinary differential equations by extending the Prelle-Singer method, J. Phys. A: Math.Gen., 34 3015-3024 (2001); L.G.S.Duarte, S.E.S.Duarte and L.A.C.P. da Mota, A method to tackle first order ordinary differential equations with Liouvillian functions in the solution, in J. Phys. A: Math. Gen., 35 3899-3910 (2002); L.G.S. Duarte, S.E.S.Duarte and L.A.C.P. da Mota, Analyzing the Structure of the Integrating Factors for First Order Ordinary Differential Equations with Liouvillian Functions in the Solution, J. Phys. A: Math. Gen., 35 1001-1006 (2002); L.G.S. Duarte, S.E.S.Duarte, L.A.C.P. da Mota and J.F.E.Skea, Extension of the Prelle-Singer Method and a MAPLE implementation, Computer Physics Communications, Holanda, 144, n. 1, p. 46-62 (2002); J. Avellar, L.G.S. Duarte, S.E.S.Duarte and L.A.C.P. da Mota, An Algebraic Analsis of Integrability of Second Order Ordinary Differential Equations., Lecture Series on Computer and Computational Sciences, v. 4B, pp 1786-1789. Theodore Simos and George Maroulis (Eds); J. Avellar, L.G.S. Duarte, S.E.S. Duarte, L.A.C.P. da Mota, Integrating First-Order Differential Equations with Liouvillian Solutions via Quadratures: a Semi-Algorithmic Method, Journal of Computational and Applied Mathematics 182, 327-332, (2005); J. Avellar, L.G.S. Duarte, S.E.S. Duarte and L.A.C.P. da Mota. A semi-algorithm to find elementary first order invariants of rational second order ordinary differential equations. Applied Mathematics and Computation, 184, p. 2-11, (2007).