OpenEuphoria

Re: More atom precision (was: Re: File size limit)

• Posted by Fernando Bauer <fmbauer at hotma?l.?om> Jun 12, 2008
• 717 views

Jason Gade wrote:
> 
> Jason Gade wrote:
> > 
> > Okay, I looked at the code again and I think that I got it right.
> > 
> > First let me say that the epsilon and exponent stuff was actually written by
> > Matt Lewis. I just "adopted" (stole) it.
> > 
> > What I realized reading the code, though, was that it wasn't a comparison to
> > -1023 that should be changed (which made little sense to me) but rather
> > this:
> > 
> > }}}
<eucode>
> >     if exp > 1023 then
> > 	    -- normalized, so implicit 1 (53rd bit) in front
> >         epsilon = power(2, exp - 53)
> >     else
> >         -- denormalized, so no implicit 1 (no 53rd bit)
> >         epsilon = power(2, exp - 52)
> >     end if
> > </eucode>
{{{

> > 
> > The original code compared to 52 and 51 respectively. An off by one error. A
> > normalized number adds an implicit 53rd bit (and therefore an extra power of
> > 2) and a denormalized number only uses the 52 bits of the fraction to
> > represent
> > the number.
> > 
> > I could be wrong, but that was my thought process, and it seems to be
> > consistent
> > at the high end.
> > 
> > I haven't tested it at the small end.
> 
> Never mind -- I think I see comparing to -1023 more clearly and more correct.
> 
> Thanks again, my understanding of FP representation has increased.
> 

Thanks Jason for our chat about this subject. As you, I think my understanding
of Euphoria and FP representation have increased too.

Best Regards,
Fernando