Re: gEDA-user: Using .global statements in GNUcap and mult

[al davis <ad151@xxxxxxxxxxxxxxxx>]

On Friday 06 March 2009, Yamazaki R2 wrote:
>  **WOW** I'm an idiot I can't believe I didn't think of that!
> I'll just add a wrapper script for my simulations to
> preprocess the netlist and merge the transistors with the m
> parameter. That should be a quick and easy solution until
> gnucap automatically does this for you. If anybody is
> interested I can post the script on the mailing list for
> everybody else to use. I'll probably just use perl for regex
> capability.

I don't think gnucap will ever explicitly combine devices like a 
preprocessor would.  What is more likely is to use a cache to 
save model evaluation time, while keeping them apparently 
separate.

If you really want a combined instance, that's what "m" is for.

This discussion leads me to believe that the Gnucap choice of 
having probes like "gm" which are really the device's state 
variables, give the value for one of the paralleled devices is 
a reasonable choice.


If you are thinking of methods of speeding up a simulation, that 
has always been a high priority for Gnucap.  I have a circuit 
here that runs (transient analysis) in 1 minute in Gnucap, set 
for speed, about 2 minutes in Gnucap, set for "spice-equivalent 
accuracy", about 3 minutes in Gnucap, with default settings, 
which are usually more accurate than Spice, about 8 minutes 
with all options set as slow as possible.  It takes 8 hours on 
NGspice.  It's a linear circuit with about 500000 nodes.  Spice 
run time is a quadratic function of circuit size.  Gnucap 
scales linearly.



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