Re: gEDA-user: [Off-Topic] pcb grid improvements... status of patch?

[Gabriel Paubert <paubert@xxxxxxx>]

On Wed, Jul 13, 2011 at 11:27:48AM -0700, Colin D Bennett wrote:
> On Wed, 13 Jul 2011 11:05:56 -0700
> Colin D Bennett <colin@xxxxxxxxxxx> wrote:
> 
> > On Wed, 13 Jul 2011 19:55:02 +0200
> > Gabriel Paubert <paubert@xxxxxxx> wrote:
> > 
> > > Great. As an astronomer, I really need to be able to define
> > > my PCB in astronomical units and parsecs :-) 
> > 
> > You'll have to wait for 64-bit internal unit storage...
> > (when metric internals [nm units] is implemented)
> 
> Correcting myself:
> 2**64 nm â 0.123 AU
> 2**128 nm â (2.3Ã10**18) AU
> 
> I guess 64-bit numbers won't do it for you!

The dynamic range of values you need for some modelling code
in astronomy is, well, astronomical.

25 years ago, I had to move some scientific code from an IBM 
370 mainframe to a VAX. The dynamic range of single and double 
precision on the nefarious IBM hexadecimal floating point was 
roughly 10^+/-76 (16^+/-64). The VAX could only reach 10^+/-38 
(2^+/-128) in both single and double precision at the time (later 
they added the so called G-float format with an 11 bit exponent 
like IEEE). It turned out that I had to be very careful and scale
several variables because otherwise I triggered overflows and 
underflows on the VAX.

I must admit that I've never run into problems with IEEE double 
precision (10^+/-308).
  
	Regards,
	Gabriel


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