kicad-developers team mailing list archive

[Andrew Zonenberg <azonenberg@xxxxxxxxxxxxxxx>]

Maybe this is related to the bug that causes two collinear tracks to not
show up as one for the purpose of measuring track length?

On Fri, 2014-04-25 at 11:29 +0200, Lorenzo Marcantonio wrote:
> Still looking at that code after the SEGVIA cleanup.
> 
> AFAIK the track/via DL-list on the board is kept sorted (or maybe only
> grouped?) by netcode, so all the segments of a net are contiguos on the
> list. Presumably the 'rebuild board connectivity' button re-sorts the
> list when something changes substantially (usually the netlist).
> 
> I'm in the 'merge collinear segments' section in clean_segments();
> inside the main 'for each track which is actually a TRACK', just after
> the flag and no_inc definitions there is a funny looking for loop
> (actually a while in disguise :D). I think the idea here is to find
> other tracks attached to the start point of the segment in exam, using
> TRACK::GetTrack(), from the next on until the end.
> 
> In pseudocode it seems to work in this way:
> 
> looping with segStart from the next of the current segment
>     find a segment from segStart on attached to the current segment begin point
>     if found:
>         if it's not a TRACE or if the width is different:
>             exit the loop
>         if there isn't another segment like the one found before:
>             set the flag
>         exit the loop
>     exit the loop
> 
> ...then proceed to process the segment found and does the same with the
> other endpoint in substantially the same way.
> 
> So... have I got it wrong? it's me or it isn't a loop at all? whatever
> happen it hits a break. I don't know the exact logic needed here, but
> shouldn't retry with another one segment if the width mismatches or it
> hits a via? why the only one segment connected? shouldn't it work in
> a tee, too?
> 
> Typical example:
>  -S1b-
> --S1--O--S2--
>       |
>       S3
>       |
> 
> (S1b is overlapping partially with S1 and ending on the via O).
> Shouldn't S1b be 'eaten' by S1. Or it is somehow detected as
> unconnected? (how? both edges are connected to S1) *OR* the routine is
> expected to only handle the case
> 
> --S1--.--S2--
> 
> (where the . is only a coincident endpoint)?  If that's what meant for
> collinear the the routing makes more sense (but then why a loop which
> doesn't ever repeat?)
> 
> Another thing:
> 
> in TRACK::GetTrack(TRACK*, TRACK*, int), if I got the idea correctly, it
> first looks walking in both the directions from the this position
> looking for a matching track, for 50 paces (probably to optimize the
> usual case) and then do an exhaustive search on the passed range.
> 
> In this function:
> 1) (only nitpicking on this:P) instead of the ugly:
> 
>     previousSegment = nextSegment = this;
>     
>     why not
>     
>     previousSegment = this->Back();
>     nextSegment = this->Next();
> 
>     so that explicit check for this are not needed?
>     
> 2) instead of doing the general search why simply don't continue the
> bidirectional walk until it its the passed limits?
> 
> 3) what if I wanted to continue the search (for example in the 'loop' of
> the cleaning routine)? with a bidirectional search you can't express it
> (unless you return also on which side you found it and keeping track of
> two search ranges).
> 
> 4) in the backward iteration, how could a TRACK* have a PCB_T type?
> isn't PCB_T the whole board?
> 
> That's a lot of questions but that section of code really confused me...
> 
> Thanks in advance,
> 

-- 
Andrew Zonenberg
PhD student, security group
Computer Science Department
Rensselaer Polytechnic Institute
http://colossus.cs.rpi.edu/~azonenberg/

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