Re: initial_step and final_step in DC sweep

Geoffrey,

First, I should say that I like the style: it is structured and readable. 
Still, I do think analysis() calls add to the comprehensability (?) of the 
code.

Your examples below obviously give the wrong, i.e. bad use of analysis 
codes. However, wouldn't you agree that analysis("nodeset"), 
analysis("static") and analysis("ic") refer more to phases during the 
simulation, irrespective of the actual simulation type? So using f.ex. 
analysis("nodeset") to restrict execution of the geometry processing and 
f.ex. analysis("static") for the thermal processing would not have the 
problems you indicate below with explicit analysis types, but would have 
the advantages of making the limited execution of these initializing 
sequential blocks explicit.

Marq


Marq Kole
Competence Leader Analog Simulation, Philips ED&T









"Geoffrey.Coram" <Geoffrey.Coram@analog.com> 
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owner-verilog-ams@server.eda.org
28-08-2006 14:01

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Subject
Re: initial_step and final_step in DC sweep
Classification







Marq -
I am, indeed, relying on compiler optimizations.

Borrowing again from my BMAS presentation, what if you did
if (analysis("noise")) begin
  // Extended noise equations (6.103)..(6.113)
end

and then ran this in a PNoise analysis.  Since "noise" matches
only standard Spice small-signal noise, you would get no noise
in a PNoise analysis.  Neither the LRM nor the compact model
author should have to worry about keeping track of all the
different types of noise analyses and explicitly coding for them:

if (analysis("noise","pnoise","hbnoise","qpnoise","xyznoise" ... //BAD!


In another case, I saw a model that had the capacitance 
equations in analysis("tran") -- meaning that there would
be no capacitance in an ac analysis, nor in PSS!


I am content to have "wildly varying run times" and I will complain
loudly to those vendors that have the longer run times.

I am not content to have discrepancies between ac and tran,
or tran and PSS, because model writers have tried to work
around limitations of the compiler.

-Geoffrey


Marq Kole wrote:
> 
> Geoffrey,
> 
> I have taken a look at your MOS11 model: I see that you have totally 
abstained from using initial_step and final_step, but also from the 
analysis functions. I assume that you're relying on compiler optimizations 
that let the separate sequential blocks only be run when none of the 
module-scope variables they use changes value. Is that correct? Doesn't 
that introduce wildly varying run times in the various simulators? 
Wouldn't analog conditional statements be a more obvious guard against 
unnecessary execution of these blocks?
> 
> Marq