Re: [ng-spice-devel] Re: snapshot/resimulate


To ng-spice-devel@ieee.ing.uniroma1.it
From Al Davis <aldavis@ieee.org>
Date Wed, 11 Apr 2001 23:00:58 -0700
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A little note on restarting.

ACS has "mark" and "unmark" commands that let you do a restart.  You 
can stop a transient analysis (control-C) and restart it.  It will 
continue from where it left off.  If you stop it and "mark", it will 
still continue from where it left off, but next time it goes back to 
the mark.

In most cases, this is not hard technically.  Backward Euler and 
Trapezoidal methods can start based on only the DC initial condition. 
 Higher order methods need more previous information, so the usual 
approach is to use a low order first step to get it going, then 
switch to the higher order method.  Higher order methods don't work 
well in simulation anyway.  "Gear-2" is a good method that requires 
two steps back, so one Euler or Trapezoid step will do it.  "Gear-3" 
and higher has more problems and is probably not a good choice anyway.

Some other devices, like transmission lines, may be harder if the 
information has been thrown away.

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