Re: gEDA-user: pcb crooked traces

[Andrew Poelstra <asp11@xxxxxx>]

On Tue, Oct 12, 2010 at 12:10:36PM +0200, Armin Faltl wrote:
> DJ Delorie wrote:
> >On Mon, 2010-10-11 at 15:25 -0700, Andrew Poelstra wrote:
> >>I think we want to allow negative locations. It would be nice to set parts
> >>outside of the pcb boundary, for example when initially placing everything.
> >
> >We limit ourselves to half so that *distances* can fit in a signed
> >same-size value.  The range of computable distances on a board will
> >always be twice the range of coordinates.  More if you do 2-D distance,
> >but we can use floating point there (we'd be doing a sqrt() anyway)
> When using signed integers for coordinates and offsets (vectors), by
> restricting to the
> positive quadrant, allowing a 2x2m board will still yield a 32-bit
> overflow, if you try
> to place a large footprint at the right edge of the board. So I
> think forbidding negative
> board coordinates doesn't guard against anything. If one wants to
> enforce range-savety,
> the boards and footprints better be +-1m maximum.
>

But if we limited everything to 2m, using unsigned integers, we'd
be okay with 32 bits. I'm not sure what you're saying here.

Having said that, I still want negative coordinates. So do we need
to limit things to 1m? Yuck.
 
> Personally I favour 32-bit integers on 32-bit machines, because I
> think that 64-bit
> emulation must be at least 3x slower than native ops. Enable 64-bit
> coords on 32-bit machines
> with a configure flag. On 64-bit machines of course 64-bit, since 32
> is probably slower.
> s
>

Well, ``probably slower'' isn't a good reason for anything. I doubt
your speculation on both 32- and 64-bit machines, so testing will
need to be done.


Andrew
 


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