[Cfp-interest 2210] Re: quantum

[Paul Zimmermann]

       Hi Mike,

someone who reads that definition will wonder what is the difference with an
ulp. It would be nice to have a document and/or web page describing the
difference between quantum and ulp (if any) on some well-chosen examples.

Best regards,
Paul

> From: "Mike Cowlishaw" <mfc at speleotrove.com>
> Date: Wed, 6 Oct 2021 13:32:28 +0100
>  
> Hi Paul,
> 
> 'Quantum' in this sense was a usage made up by the 754 committee, and I
> don't think I ever used it before 2003 or thereabouts (e.g., in
> http://speleotrove.com/decimal/damodel.html).
> 
> 754 defines it as 
> 
>   "quantum:  The quantum of a finite floating-point representation is the
> value 
>   of a unit in the last position of its significand.  This is equal to the
> radix
>   raised to the exponent q, which is used when the significand is regarded
> as an 
>   integer."
> 
> I generally talk about 'preserving the exponent' rather than 'preserving the
> quantum'.
> 
> Mike
> 
> 
> 
> > -----Original Message-----
> > [this is maybe more a question for the IEEE 754 list, but 
> > since the intersection is not empty, and this list is more 
> > active, I ask it here]
> > 
> > I searched yesterday for a wiki page explaining the notion of 
> > "quantum"
> > in the context of IEEE 754-2019, with some examples, but found none.
> > 
> > Maybe there is one and I did not find it because my search 
> > engine thought I was looking at something related to quantum 
> > computers.
> > 
> > If there is none, this is really something missing.