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

[r <nbs.public@xxxxxxxxx>]

On Tue, Mar 10, 2009 at 2:11 PM, al davis <ad151@xxxxxxxxxxxxxxxx> wrote:
>
> Can you send me some examples of where it crashes?

I sent you a bug report recently. As for the newest revision, I
haven't tried it yet, sorry.

>> ability to probe signals at lower levels of hierarchy,
>
> You can.

How to do it without adding probing devices to the circuits? Or, how
to save all signals or all classes of signals?

>> robust operating point analysis etc.
>
> Can you send me some examples of where it doesn't work?

I sent it to you a while ago (an example with a simple CMOS opamp).
Your conclusion was that OP analysis failed because of missing
homotopy.

>> As for the simulation performance, there are many things to
>> improve as well. Gnucap still doesn't support gear
>> integration method,
>
> yes it does.

Sorry, I missed this addition. Yes, Gnucap supports gear method. I'm
going to try it out soon.

>> its transient simulation time step
>> control is very brittle
>
> Really?  can you give some examples?  I don't have access to the
> big-bucks simulators for comparison, but in my tests the time
> step control is consistently better than Spice.

Earlier last year I did a bunch of tests using clocked CMOS digital
circuit - they tend to exercise time step control quite well. I didn't
even need other simulators for comparison - just analysing output data
was enough to see how the time step control algorithm performed. It
was fairly difficult for me to tune Gnucap options so that it scaled
time step "reasonably" without causing excessive errors or ringing.
Again, I'm going try the newest version of Gnucap, including its gear
method.

>> and output data are saved in
>> non-indexed text files.
>
> Eventually, the output will be through plugins too, so you will
> be able to add other formats.  For now, I had to put a stop to
> new features to focus on making an official release.

That's OK. Perhaps even I can help you with this someday. My point is
that it's a bit early to advertise performance of the tool, when many
important bits of functionality are still missing. E.g. text file
format may be great for simple simulations but it isn't terribly
useful for long running simulations (i.e. those which need a fast
simulator).

BTW., you are probably aware of a renewed interest in high performance
analog simulators (not mixed-signal and not "fast-spice" type). Guys
are trying to parallelize as many operations as possible (evaluating
models and matrix operations) and optimize all other bottlenecks (time
step control, IO). If you want to compete in this field it's going to
be tough now. However, even with lower performance Gnucap can still be
a very valuable tool as long as it does its job. People often want to
run many small simulations in parallel and in such scenario other
simulators can be very pricey.

Regards,
-r


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