Re: modelgen & veriloga

[Vincent Pinon]

Hi Felix, many thanks for the detailed answer!

Le 2/25/20 à 2:01 PM, Felix Salfelder a écrit :
> Verilog-ADMS only contains a subset of Verilog-A, and adds other things.
> Verilog-AMS is a superset of Verilog-A,
> and gnucap has been designed with mixed signal in mind.
I'm aware of that :) I would target verilog-a 1st to get compact models 
to work,
then extend to AMS.
> The spice templates produce code that computes matrix stamps and current
> contributions. These represent voltage controlled current sources, and
> there is considerable overhead in the templates that relates to
> simulator internals.
Simulation speed rapidly matters, so we should directly go with 
something efficient
> "ddx" is where I gave up -- it was not fun anymore, when
> changes to adms internals were required.
I understand!
> What we really need to break the deadlock is
> gnucap-modelgen-verilog.
Is there anything existing beyond an empty repository?
>   I suggest to implement it one step at a time
> and reuse as much as possible. In a nutshell that is
>
> - a simple verilog parser. like mg_in.cc (to grow as/where needed).
>    lex/yacc looks compelling, but it can be a can of worms.

I had seen that yosis parses verilog with lex/yacc rules; however I have 
read that these tools also produce quite heavy code.

Currently, lang_verilog doesn't use anything external? I'm balancing 
between not re-inventing and not over-engineering thing...

> - make a subcircuit with components in it, and deal with parameters.
>    relatively straightforward, but helps with understanding gnucap.
>    (carefully avoid MODEL_CARD)
So we would go for a "subcircuit" architecture, not trying to plug 
directly into matrix? I understand it is more generic & flexible, is it 
as efficient?
> - implement some Expression infrastructure (c.f. m_expression.h)
>    we need some derivatives and dependency tracking. partly nontrivial.
What do you mean with "dependency"?
> - eject components for @analog block. much like modelgen.  perhaps use
>    or recycle the voltage and current sources from gnucap-adms.
You mean pass over "subckt" instances?
> - support dynamic expressions, ddt/idt/ddx
>    likely more nontrivial, but this is what you need for "verilog-A".
> - (whatever I forgot)
> - disciplines, logic blocks, connect modules, cross events
>    intersects with other work in progress. only a matter of time.
Finish line not in direct sight :)
> - make it run faster, in many ways.

Faster than what? ADMS?

How?

> Certainly a challenge. I am happy to discuss details. Please feel free
> to ask. Al might have more to say about it.
>
> cheers
> felix

Many thanks again!


Vincent