yade-dev team mailing list archive

[Jerome Duriez <jerome.duriez@xxxxxxxxx>]

As for history/archeology, it looks like Vaclav introduced this code [*] 
(completing the previous commit [**])

I'd thus propose to get rid of ZERO_TOLERANCE at least, replacing with 
EPSILON where it is currently used.


Thoughts ?


(As for me, tolerance would for instance be  useful to know when an 
increasing value (x, increasing from x0 < a) can be detected as entering 
an interval [a,b], accounting for a possibly blurred comparison between 
x and a. Would you consider this as very specific ? :-) )


[*] 
https://github.com/yade/trunk/commit/2172ceb5af8704bf5073f82acfdd8686c89d3c99
[**] 
https://github.com/yade/trunk/commit/6e5e0a8d1e8008855109bd28bd7098129026f2d2

------
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On 15/11/2018 16:21, Bruno Chareyre wrote:
> Hi Jérôme,
> I don't know, but I guess they were introduced independently by 
> different authors.
> I actually don't know why we would need to define tolerance at all, 
> unless in very specific cases.
>
> For instance I judge that a line like this (ViscoelasticPM.cpp) is not 
> only useless but actually wrong:
> if (std::abs(cn1) <= Mathr::ZERO_TOLERANCE ) cn1=0;
>
> If it's small let it be small. No need to make it zero. And since cn1 
> is not dimensionless it implies that currently the accuracy depends on 
> a specific choice of units...
>
> Bruno
>
>
>
>
> Bruno
>
> On 11/15/18 3:54 PM, Jerome Duriez wrote:
> > Hello,
> >
> > Out of curiosity, why do we have both Mathr::ZERO_TOLERANCE and 
> > Mathr::EPSILON in the code [*] ?
> >
> > I would understand they're both intended to give an expected 
> > magnitude of rounding errors. (Note that ZERO_TOLERANCE is hardcoded 
> > as 1e-20, while EPSILON is ~ 2e-16 here)
> >
> > Both are used throughout the code (EPSILON more often ?)
> >
> >
> > Thanks,
> >
> > Jérôme
> >
> >
> >
> > [*] 
> > https://github.com/yade/trunk/blob/3269232e4982c1aa527581a200a0224555b09a1e/lib/base/Math.cpp
> >
> > ------
> > Chargé de Recherche / Research Associate
> > Irstea, RECOVER
> > 3275 route de Cezanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE
> > +33 (0)4 42 66 99 21
> >
> >
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