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

[P Zoltan]

   Hi,

  here is a patch that makes ktechlab to use Eigen for calculations, so the  
internal matrix implementation can be removed.

  Steps to use:
  1. patch the source. If it fails, tell me, because I haven't tested the  
patch :D
  2. download and extract eigen somewhere. I've used version 2.0.3. (Note:  
see a comment in the patch about an eigen bug -- we should use a newer  
version when we import eigen in ktechlab )
  3. in kdevelop, in the automake manager, add the path of the extraced  
eigen sources to the includes. This should be done for all subfolders...
  4. compile
  5. run

  Known problems:
  - the caching and changed/unchanged flags probabily don't work as they  
should
  - 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...

  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?)
        run logic (here -- why?)
        check for convergence
   else
     solve as a linear system
   run logic

  (where are the components updated?)


  All the above shoudl be clearly defined, an only after, starting to  
test/refactor the implementation

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