Re: [Libmesh-users] Syncronize a vector among processes

[Renato P. <re...@gm...>]

Ok, I see Roy's point.

Let's start over.

I have a DG system (duplicated DOFs).
I calculate the aperture at the DOFs sharing coordinates
(position_at_the_element _minus_ position_at_the_neighbor).
I do that for all integration points.
I need an ordered vector with the bigger apertures first, and I need to
identify who they are (element, neighbor and integration point).

I think (not sure) it *is* indeed a maxloc() problem, as long as I can have
my own objects to be compared with a specialized "operator<".

(I tried to get closer to "X" here ... helped?)

Thanks
Renato



On Thu, Jun 28, 2018 at 1:08 PM, Roy Stogner <roy...@ic...>
wrote:

>
> On Thu, 28 Jun 2018, Renato Poli wrote:
>
> Should I copy-paste code from NumericVector to build mine?
>> Any suggestion?
>>
>
> We're pretty far into XY Problem territory at this point.
>
> http://xyproblem.info/
>
> What you've said about your vector is that you'll need to be able to
> do a maxloc() on it, that it's describable as a "solution vector",
> that you seem to interested both in sorting it and in using it with
> an arbitrary value type T.  That's not enough information to give
> advice.
>
> The "arbitrary value type T" criterion rules out pretty much all of
> the libMesh NumericVector subclasses (except perhaps
> DistributedVector, with some work), but the "solution vector"
> description in the libMesh context *implies* a NumericVector subclass
> (and not the DistributedVector subclass, if you're solving an implicit
> system).
>
> Another alternative is to sync the solution vector to all processors so
>> that everybody can do the same calculation.
>>
>
> Are you referring to the maxloc() calculation here?  That wouldn't be
> hard to add to NumericVector (with specializations for speed in
> subclasses), and the implementation would be a lot more efficient than
> serialization.  But maxloc has nothing to do with the "you can't use
> NumericVector with generic type T" problem, so maybe back up and
> figure that out (starting with *why*, not *how*)first?
> ---
> Roy
>