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> Date: Sun, 21 Aug 2016 10:17:41 -0500
> From: royst...@ices.utexas.edu
> To: marchy...@hotmail.com
> CC: libmesh-users@lists.sourceforge.net
> Subject: Re: [Libmesh-users] what is the deal with TypeVector size()?
>
>
> On Sun, 21 Aug 2016, Mike Marchywka wrote:
>
>> It apparently is a deprecated way to get a norm which would seem at odds
>> with both math and programming conventions.
>
> That is in fact why it's deprecated, yes. It's been deprecated long
> enough that we should probably remove it entirely in the next release;
> old users should have had time to change over by now and new users
> would be better served by a compile-time failure instead of a run-time
> warning.
>
>> Further, AFAICT, it is always 3D
>
> It's always LIBMESH_DIM dimensional; a constant defaulting to 3 and
> set at configure time. Usually 2D problems are cheap enough that
> people don't bother to worry about optimizing them, but there's
> occasionally someone who has to run a zillion 2D problems as the inner
> part of an optimization or uncertainty quantification loop and so we
> try to keep --enable-2D-only from regressing.
>
Just offhand this seems like something suited for templates. While the
efficiency issue may be minor it seems more natural to use templates
here rather than sizes defined at lib build time. At least provide a loop limit
that returns the constant where ever defined. size() const { return
LIBMESH_DIM; }?
But again templates are there and things like 2D cross products can assume
a zero z and return something with a 3rd component. I suppose a 3D vector
if constructed with a 2 D ctor could just consider itself 2D and anyone who
does not care can loop over the zero third D.
The examples seem to use lots of compile time constants and AFAICT right now,
I would not mind at all recompiling to add a new species to a simulation. And
the same
would be fine for dimensions just not rebuilding the whole lib or having a
second to
link against when I may want to mix and match. Say for example having a 2D
and 3D system that interact in some way that you may want to do them in
isolation
and then iterate until they are consistent with each other. Would this never
occur?
>> forcing an anyone wanting to use it would have to know otherwise how
>> many matter or just loop over wasted zeroes.
>
> Right.
So what is the best way to iterate over components? Use LIBMESH_DIM?
Thanks.
> ---
> Roy
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