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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 
>

-- 
----------------------------------------------
Jörg Schaber
Max Planck Institute for Molecular Genetics
Ihnestrasse 63-73, 14195 Berlin, Germany
Phone: +49 30 804093 19, Fax: +49 30 804093 22
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