Re: NDSolve precision and velocity problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg91318] Re: NDSolve precision and velocity problem*From*: Joerg Schaber <schaber at molgen.mpg.de>*Date*: Fri, 15 Aug 2008 06:53:50 -0400 (EDT)*References*: <g81378$o$1@smc.vnet.net> <48A43754.1000105@gmail.com>

Thanks. Actually, I tried Method->"Adams", but after 10 minutes waiting I gave up. BDF seems to work fine though. I did't see it in the Documentation. Jean-Marc Gulliet wrote: > Joerg Schaber wrote: > >> I have an ODE system that takes lots of time to solve with NDSolve >> (several minutes), >> whereas the same system with the FORTRAN solver LSODA >> solves the problem in an second. >> When I decrease the precision, e.g. AccuracyGoal->6, NDSolve crashes. >> It often crashes, because it finds complex values in a >> less-than-comparison. >> >> Maybe it's a method problem. >> How do I tell NDSolve, to use the same methods as the LSODEA solver? > > If by the above you mean using either Adams or Backward > Differentiation Formula (BDF) methods [1], for nonstiff or stiff > cases, respectively, you can use the option *Method*. > > The following might be worth reading (or at least browsing): [2, 3, 4] > > Regards, > - Jean-Marc > > [1] "LSODE", _Serial Fortran Solvers for ODE Initial Value Problems_, > https://computation.llnl.gov/casc/odepack/odepack_home.html > > [2] _IDA Method for NDSolve_, > http://reference.wolfram.com/mathematica/tutorial/NDSolveIDAMethod.html > > [3] "Adams methods", _NDSolve Method Plug-in Framework_, > http://reference.wolfram.com/mathematica/tutorial/NDSolvePlugIns.html > > [4] _Monitoring and Selecting Algorithms_, > http://reference.wolfram.com/mathematica/tutorial/MonitoringAndSelectingAlgorithms.html > -- ---------------------------------------------- JÃ¶rg Schaber Max Planck Institute for Molecular Genetics Ihnestrasse 63-73, 14195 Berlin, Germany Phone: +49 30 804093 19, Fax: +49 30 804093 22 ----------------------------------------------