[Ktechlab-devel] Converting to Eigen - patch for revision, ver.1

[Zoltan Padrah]

2009/8/9 Alan Grimes <agrimes at speakeasy.net>

>
> P Zoltan wrote:
> >  here is a patch that makes ktechlab to use Eigen for calculations, so
> > the internal matrix implementation can be removed.
>
> =)
>
> >  Known problems:
> >  - the caching and changed/unchanged flags probabily don't work as they
> > should
>
> I think that's where your memory leak is. It tries to cache everything
> and runs out of memory.
>
Memory leak? I have of that, too?


> >  - when inserting a reactive element in the circuit, the cpu usage will
> > increase to 100% after a time. Probable causes are that eigen uses great
> > precision calculation, so the circuit will never enter in steady state.
> > Or just some caching problem...
>
> >  Todos:
> >  - test it :D
> >  - we'll have to define _clearly_ the algorithms and data structures
> > used in the cirucit solving process. Currently I don't know how the A, b
> > changed flags should work and what is the purpose of CNode and CBranch
> > classes, how/when the iterations shoud be done, and so on...
>
> When the circuit is in a steady state, it doesn't make any sense to
> recompute LU. (simply solve LbU = x ) or something like that.
>
> Note: the function call you make "mp_lu->rank() == 0" is equivalent to a
> correct version of my "validate()" function. Ie, when rank = 0, the
> matrix is singular/invalid/unsolvable. -- IIRC. Since I'm a dunce, I
> hacked together the validate() function in an attempt to detect bugs in
> the components as early as possible. asking "rank() == 0?" does the same
> thing.

Yes, I know. Still, that rank() call should be removed, as LU::solve()
method returns false if it can't solve the equation system. That case is not
addressed -- the question is what to do in that case: write a "?" for
voltage level, or use the last valid state for the circuit?


>
>
> >  Here is the sketch of the algorithm (should be extended...):
>
> > if a component is added, removed, connected, ... in the circuitdocument:
> >  split the document in circuits, by connectivity
> >  create elementset from the circuit
> >     create the matrix corresponding to the elements
>
> > a step in the simulator:
> >   if the circuit contains nonlinear elements
> >     solve the cirucit by iterations
> >      in each iteration
> >        call the handler of nonlinear elements
> >        recreate the LU of the eqation matrix
> >        update nodes (why?)
>
> Could you point me to a class, method and line number for that so that I
> can explain it?

In not that interested in a particuar class, but in the interaction of all
the  classes; or just the algorithm, without any particular class/method.


>
>
> >        run logic (here -- why?)
> -- cuz you could have triggered a state change.
>
> >        check for convergence
> >   else
> >     solve as a linear system
> >   run logic
>
> >  (where are the components updated?)
>
>
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