Re: gEDA-user: pcb crooked traces

[karl@xxxxxxxxxxx (Karl Hammar)]

John Doty:
> On Oct 9, 2010, at 5:41 PM, DJ Delorie wrote:
> >>> I'm surprised we're still discussing this *at all*.
> >> You can't build a solid system on a shaky foundation. This is
> >> precisely the kind of thing we need to get right, or it will
> >> continue to cause unexpected artifacts to appear.
> > I think we got it right the first time we discussed it way back when.
> > We're just rehashing old arguments, no new info is being added.  I
> > know what we're going to do, and we all seem to agree it's the right
> > thing to do.  Where is this "shaky foundation" you're accusing us of?
> I'm not accusing. The point is that this is apparently important,
> and hasn't been done yet. I'm not sure there is agreement.

I'm also very surprised that we are still discussion this.

I got into this thread due to some faulty assumptions about floats.
The rationale is that if I do something, it should be for the right 
reasons, not for any bogus reasons.

The claims about floating point so far are:

1, they have too great rounding error
2, equality operator ("==") is unusful
3, integer arithmetics is for the performance of it

Well, I/we have found out that
1, the rounding error is less than the size of an atom
2, so is any integers eqaulity operator when 1 == 1 nm
3, the gain isn't 100times, not even 10 times, it's a mere one digit 
   figure, and the bottlenet is elsewhere

Up to now my only intent in this has been to say "that claim is false", 
nothing else. But now I'm starting to feel that using integers is 
actually the root cause of the "jagged lines" and mil/mm problems.

On the downside for integers we have, if I may cite John Doty:

  "There are subtle problems with carrying real number analytic
  geometry into a discrete domain."

So far I have not found any good reasons for using integers, and John 
has presented a wery good one for NOT using them. If we can get rid of
thoose "subtle" problems, we will have a more healthy program and it
will also be easier for new developers to join (in that part).

Yes, there is one reason against a change to doubles since that would 
force us to reevaluate the formulas, and that is hard work.

Regards,
/Karl Hammar

---------
Aspö Data
Lilla Aspö 148
S-742 94 Östhammar
Sweden
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