Re: Fw: Contributions (was Re: disallow distributed switch branches)

Kevin -
I was somewhat sympathetic to your request to easily be able to
short a pair of nodes, knowing only the hierarchical path to them:

   V(a.b.x,a.b.y) <+ 0.0;

It seems like a reasonable thing to want to do.

However, this causes too many problems in other areas because of
the fact that it's an OOMR.  If I have a bipolar transistor model
that's been compiled previously, and then in a new design, I
decide to short the b-e junction
    V(top.i1.ibias.b, top.i1.ibias.e) <+ 0.0;
then this would require re-compiling the BJT model!  (Generally,
compact models are written with I(b,e) <+ ..., and in any case,
your most recent post (below) said you want the compiler to
collapse the nodes.  Either way, you've changed the topology
of the BJT and perhaps even a larger module that has been
pre-compiled.)

David's suggestion:
> > What I had in mind was:
> > I(a.b.x,a.b.y) <+ V(a.b.x,a.b.y)*Gshort;

is nice, and does *not* add rows to the matrix; a voltage source
always does because you need an extra unknown for the current
through the source (unless you collapse the nodes -- but how
does the simulator know that your 0-v source isn't really an
ammeter? in which case collapsing the nodes means you lose
the ability to probe the current).

-Geoffrey



Kevin Cameron wrote:
> 
> But basically you are proposing a "hack" to fix a language deficiency.
> If the user asks for a short-circuit (or fixed voltage) I see no reason
> not to give it to them. It might cause the simulator problems, but it's
> easier for other tools to work out a short-circuit is what is intended -
> i.e. the simulator vendor can fix this "under the hood" with resistors
> if they want, but the user should not have to do it. If it's
> recognizable as a static assignment the compiler can collapse the nodes.
> 
> Kev.

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