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Date: Wed, 12 Dec 2012 11:28:27 +0100
From: Gabriel Paubert <paubert AT iram DOT es>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Find rat lines
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On Wed, Dec 12, 2012 at 07:25:52AM +0100, gedau AT igor2 DOT repo DOT hu wrote:
> 
> 
> On Tue, 11 Dec 2012, Peter Clifton wrote:
> 
> >Yes - had a fear it might be complex.
> >
> >That doesn't mean it is intractable though,.. board auto-routing is a NP
> >complete problem, but we still do a reasonable job.
> 
> I agree. My point is: finding a clean solution backed up with graph
> theory (proven to work on all cases perfectly) needs a very
> different approach than finding a set of good-enough methods and
> heuristics to get a pretty good result in most of the cases. At
> least according to my experience with such problems...
> 
> >
> >>There were some alternative ideas, mostly improvements of the propagation
> >>idea; instead of finding a single object to blame, it may highlight a
> >>longer set of lines in a way that it is very likely to contain the part
> >>the user is interested in, but this needs some more thinking.
> >
> >It is probably impossible to identify a single (or list of) object(s)
> >which is/are to blame in any general case we encounter. There might be
> >multiple solutions to resolve the short. We just need to try to provide
> >helpful information to the user so she may resolve the issue.
> 
> Agreed. I'd further refine this part: in case we find the problem is
> NP, we can safely tell we won't come up with a perfect solution and
> then we could concentrate on one(s) that come(s) up with reasonable
> results for the most common cases. Or even, results better than what
> we have now.
> 
> >
> >
> >I'm trying to think of the class of mistakes I make when causing
> >shorts..
> >
> >1. Dragged random object out of place (or moved instead of
> >rubber-banded).
> >
> >2. Applied thermal to wrong layer
> >
> >3. Had inappropriately tagged / named mechanical layer short across some
> >pins or vias.
> >
> >4. Routed tracks after (1, 2 or 3), compounding the issue with more
> >cross-connected geometry. This will probably be in the form of wiring
> >some pins / pads to the wrong track, or to adjacent pins on the shorted
> >net. It might (occasionally) be due to adding more thermals to the wrong
> >layer.
> 
> 5. random modification somewhere that modifies how polys are
> separated; for example deleting a long trace that used to separate
> two smaller polys in some unseen corner.
> 
> 6. random mod of lines that modifies dicing of a poly
> 
> 7. component rotated - i obviously get this 50% of the cases with
> resistors

Speaking of this, for all (to my knowledge) resistors, most (but not all) 
inductors and most (but again not all) unpolarized capacitors, would it 
be possible to have a "symmetric dipole" attribute that means that the 
2 pins are interchangeable. I'm somewhat fed up of rotating these components 
by 180 degrees because they come with the wrong orientation (this often involves 
rotating again the reference designator so that the orientation stays the same).

Another option would be to have the ability to rotate a component without 
moving the reference designator (using the Ctrl key for example in the GUI).

Sorry to hijack this mathematical thread with this minor request...

	Regards,
	Gabriel