Re: [boost] Re: Re: Physical quantities

From: Matthias Schabel (boost_at_[hidden])
Date: 2004-01-12 22:22:43

> In all of these cases, a dimensions/unit framework that does NOT allow  
> implementation of user defined dimensions and units would be useless  
> to me personally.  I don't think that I use SI or even CGS anywhere  
> within my code: I use a mix of non-dimensionalized calculations and  
> "natural" physical units.

A demonstrative code snippet of what you would like to be able to do  
would be really helpful...

> My code is either done running in less time that it takes to compile  
> (short code that would only benefit from nearly zero compile time  
> overhead) or already runs for hundreds of hours (and hence would want  
> a zero runtime overhead, a far more important constraint for those  
> applications where I would consider using the units framework).

This is spanning the spectrum.  As it stands now, it's possible to have  
a fixed set of units which compiles quickly or an arbitrary system  
which compiles slowly.  I'm guardedly optimistic that I'll be able to  
improve compile times for the latter, but it will never be as fast as  
the fixed unit set, unfortunately...

> Numerical accuracy (which I assume you are talking about ... an  
> inaccurate dimensional analysis framework would hardly be useful :-)   
> is certainly not in the purview of the DA/units framework ... that has  
> more to do with the selection of algorithms, rescaling techniques, and  
> underlying numerical types.....

I agree - those issues should lie in the domain of the underlying value  
type.

------------------------------------------------------------------------ 
---------------------------
Matthias Schabel, Ph.D.                           	
Utah Center for Advanced Imaging Research
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mschabel at ucair med utah edu