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Subject: Re: [geda-user] Find rat lines
From: John Doty <jpd AT noqsi DOT com>
In-Reply-To: <alpine.DEB.2.00.1212141116350.26605@igor2priv>
Date: Fri, 14 Dec 2012 09:37:47 -0700
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On Dec 14, 2012, at 3:36 AM, gedau AT igor2 DOT repo DOT hu wrote:

> 
> 
> On Fri, 14 Dec 2012, John Doty wrote:
> 
>> 
>> On Dec 14, 2012, at 2:15 AM, gedau AT igor2 DOT repo DOT hu wrote:
>> 
>>> How do you _exactly_ define/calculate network affiliation? That was the original problem for the non-history case, so don't just assume it is solved, solve it.
>> 
>> How about having the user affirmatively declare it before drawing? Touch a known object, or select from list, or type netname (could implement all of these). Prominently display the netname under construction in status somewhere.
> 
> Finally, after so many emails, an idea... Let the user tag each object manually.
> 
> This would be a valid solution, but I don't see the benefits. First of all, it would be very expensive (a single line in gschem often translates to dozens of objects in PCB). At the end, it could help the user by remembering user intentions. 

It helps the user by making it clear what's happening.

> Unfortunately this leaves many of the problematic quesitons unanswered. Corner cases:
> 
> 1. The user loads a new netlist - copper areas totally valid for connectivty are highlighted as shorts

But there's no reliable way to determine what's valid automatically. You're stuck with unreliable heuristics if you try.

> 
> 2. Assume 3 networks, A, B and C; A and B has a long parallel pair of traces and connects exactly the pins they should (no short); the copper of C also connects what it should, but it crosses the long parallel lines of A and B. What should be highlighted and how did the software decide to get that result? More importantly, how would it be more useful than what
> other proposes would highlight?

You highlight the places where C touches A and B. The idea that the software should highlight shorted *objects* makes no sense, since short circuits are not a property of objects, but of their geometric relationships.

> 
> 3. Two networks, A and B, parallel for a long time, then crossover, and parallel again. Same questions as for 2.
> 
> 4. How do you handle untagged objects?

If a conductive object unaffiliated with any net touches any other conductive object, that's a short. Same as in the real world where, for example, a wire touching a floating enclosure is to be considered a problem even if there's no immediate smoke.

> 
> 
> 
> By the way this method is already possible on single sided boards using layers - each net can have its own layer. Most probably because of the extra effort involved I can't recall seeing anyone doing this, except for some of the most important/crowded nets (GND, VCC).
> 
>> 
>>> Just highlighting everything what is in short is possible with the old behaviour: press F over a shorted net. This is exactly what we want to refine, as it is not helpful on complex boards.
>> 
>> But of course that doesn't work because there are no primitive objects with known net affinites, so F can't identify the specific points where the problem is. And part of that problem (and to me, a source of great confusion) is a lack of primitive objects in the first place.
> 
> Nope. You didn't understand what I said: highlighting too much (everything that participates in the short), is not helpful, this is my main statement.

Highlighting the participating objects is not helpful. Highlighting the points of contact would be very helpful, and is intuitive if you've looked for shorts in the real physical world.

> If you can put your hatred away for a moment,

What hatred? There's no hatred here.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd AT noqsi DOT com