From: Bastien ROUCARIES <roucaries.bastien@gm...>  20071229 12:19:01

Le samedi 29 d=E9cembre 2007, Stefan Jahn a =E9crit=A0: > Am Mi, 26.12.2007, 09:15, schrieb Clifford Wolf: > > Hi, > > Hello! > > > I'm still playing around with multivibrators in transient simulation. > > This one is nice: attached you will find two identical schematics which > > produce almost the same netlist. The only difference between the netlis= ts > > is the order of the statements. But the results of the transient > > simulation are very different. (the first one fails after producing > > moreorless accurate results and the other one runs thru but nothing > > vibrates..) > > > > I think the problem is that in the 2nd case the evaluation order of the > > nodes is different so the transistor is evaluated after the value of its > > base contact has been calculated, overwriting the initial DC value I ha= ve > > set using the label. Which is quite strange because I thought that my > > label > > would cause the initial dc analyses to charge the capacitor on this wire > > so > > the wire should stay longer on a high voltage that just for step 0. > > > > Whats the error in my understanding of what's going on when doing a > > transient simulation of this circuit? > > This one is also known... And an ugly one, I know. > > Right now the position in the netlist in fact determines somehow, how > nodes are put into the circuit matrix to be solved which in turn may > affect the result due to numerical issues. > > One of the solution of this problem may be to find a way to reorder > the matrix to be solved in a way to > > 1) get a deterministic ordering > 2) and find an order which makes the matrix "easier" to solve > > If someone on the list has a better clue than me right now how to > achieve (2) then please tell me. In the qucsator core there is > already an sorting algorithm, but this just cares about pairs of > +1 and 1 (e.g. voltage sources) and not about the actual node > order... Could you please give me the equation to solve? I suppose it is an inversion. IF so the magic key is preconditionning. I can try to help when I will come back form vaccation (ie 2008/01/08). Regards=20 Bastien > Cheers, Stefan. > > >  > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2005. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > Qucshelp mailing list > Qucshelp@... > https://lists.sourceforge.net/lists/listinfo/qucshelp =2D=20 "ROUCARIES Bastien" roucaries.bastien@...= com =2D= =2D DO NOT WRITE TO roucaries.bastien+blackhole@... OR BE BLACKLISTED 