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Index reduction and dynamic state selection

Index reduction and dynamic state selection

Hi all,

I'm looking for a description of the new state selection algorithm and its implementation in the C backend. I believe that what I want is a description of the algorithm as it exists in 1.9 beta and later.

Thanks for your help,
Jim

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Re: Index reduction and dynamic state selection

Building on my prior request for information, a description of each field in the JacobianMatrix and JacobianColumn from BackEnd/SimCode.mo would also be extremely helpful.

Thanks again,

Jim

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Re: Index reduction and dynamic state selection

Hi Jim,

the actuall state selection implementation is based on

Mattsson, Sven Erik and Söderlind, Gustaf: Index reduction in differential-algebraic equations using dummy derivatives, SIAM J. Sci. Comput., url = http://dx.doi.org/10.1137/0914043.

Based on means the implementation consider some Modelica Specific Issues like StateSelection and is not yet finally. The one think that is missising is a complete check for singular systems. 
A description of the implememented algorithm is not yet availible.

Which one of the jacobian do you mean. There is a jacobian for the linearized system, one for the nonilinear sytems, one for pivoting for dynamic state selection?

Jens

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Re: Index reduction and dynamic state selection

Hi Jens,

Thanks for the quick reply. I'm interested in i) how to reconstruct the jacobian for dynamic state selection from the information in the JacobianMatrix structure and 2) what information is stored in the fields of the StateSet structure in SimCode.mo.

Thanks again,

Jim

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Re: Index reduction and dynamic state selection

Hi all,

I'm also interested on this topic.

Mattsson, Sven Erik and Söderlind, Gustaf: Index reduction in differential-algebraic equations using dummy derivatives, SIAM J. Sci. Comput., url = http://dx.doi.org/10.1137/0914043 is really interesting. Is there more useful information?

As Jens said, more information about checking singular systems is missed. Could you recommend me more bibliography about this subject?

Thanks!!!

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Re: Index reduction and dynamic state selection

Mattsson and Söderlind speak about an "elimination process of Gaussian type".

Does OpenModelica implement it? I suppose not because OpenModelica crashes simulating this model:

model singular
  // Variables
  Real y(start = 1.0);
  Real x(start = 0.0);
equation
  der(x) + time * der(y) = time;
  x + time * y = time;
end singular;

Where can I find more information about this topic?

Thanks in advance!!

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