On Mon, Jun 20, 2016 at 8:31 AM, Roy Stogner <royst...@ices.utexas.edu>
wrote:
>
> On Fri, 17 Jun 2016, David Knezevic wrote:
>
> > I guess you are saying that this reference length is rarely the
>> appropriate choice?
>>
>> Yeah, that's a bad choice. If both points (x and y) are near the origin,
>> then that tolerance will be super small. If both points are
>> far from the origin the tolerance will be super large.
>>
>> As a result, my preference would be to remove relative_fuzzy_equals from
>> the library.
>>
>
> ...
>
> OK, I'll be interested to hear Roy's thoughts on this.
>>
>
> relative_fuzzy_equals isn't appropriate for comparing points, for the
> reason you state. (for the same reason, floating-point arithmetic
> isn't appropriate for points, and I sometimes fantasize about a
> fixed-point operator-overloaded data type for them, but that ship is
> long-since sailed)
>
> relative_fuzzy_equals is a useful shorthand when comparing distances
> *between* points. And I just went through the library, and that is
> what we're doing with it. Foo::has_affine_map() compares vectors
> between points on edges, FE::reinit() compares relative positions of
> nodes.
>
> So we definitely don't want to remove it. If you want to fix up its
> currently-inadequate documentation, though, I'm all ears.
>
OK, got it, that distinction makes sense. It would be good to add these
comments to the header file at some point, I think, because I've seen
application codes where people use relative_fuzzy_equals inappropriately
(which was my original motivation for starting this thread).
Thanks,
David
------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are
consuming the most bandwidth. Provides multi-vendor support for NetFlow,
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports. http://sdm.link/zohomanageengine
_______________________________________________
Libmesh-devel mailing list
Libmesh-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/libmesh-devel
