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Re: DAE daspk solver problem

From: Lazy_Tom
Subject: Re: DAE daspk solver problem
Date: Sat, 29 Oct 2016 07:13:11 -0700 (PDT)

Sebastian Schöps wrote
> Lazy_Tom wrote
>> I don't know why DAE solvers index capabilities are not reported in
>> Octave manual. Matlab at least tells you that you can go no further than
>> index 1 (at least without doing some "magic"...)
> You are right. Feel free to oben a bug report at savannah, maybe
> immediately suggesting a string that can be added to the help. However, I
> assume that dassl and daspk will be deprecated in some future version
> since we are moving to odeXY compatible solvers.

Hi Seb.

Oh, so there are other solvers that support full implicit ODE form? I see,
any chance you can send me some links like you did for Radu 5?

About bug report, I don't know how to do it and I don't understand the
"suggesting a string" (string = comment?), can you give me more details? Or,
considering future deprecation

Sebastian Schöps wrote
> Lazy_Tom wrote
>> about the paper you cited, yup, I'm aware of it and I agree, it is quite
>> nice. 
>> Well, at least I'll gave it a try, I think that for DAE problems I'll
>> move to openModelica
> I think that ode5r from odepkg should be able to solve index3 problems
> since its based on Radau 5 [1]. We hope to have a new release of odepkg
> quickly after Octave 4.2. I will keep in mind to include such information
> in the help.

I will probably give Radau a go, assuming I understood how to set up odeset
Cheers for the index info

Sebastian Schöps wrote
> Regarding openModelica: yes, they do some clever tricks for higher index.
> As far as I recall it's based on dummy derivatives [2]. Such stuff is
> easier for modelica since it is in some sense a symbolic language.
> However, to my best knowledge, it is not really well suited for big
> problems. So, as usual, the best choice depends on what you want to do :)

Indeed. About index reduction, at the moment I can see it has three methods
(except for the third, no idea what the others mean): Uode, Dynamic State
Selection and Dummy Derivatives

BTW, nice link!



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