[petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?

[Barry Smith]

  Shri,

    If you provided your graph in parallel I suspect that the GlobalToLocal and LocalToGlobal would not work as you expect and put everything in the appropriate place.

    I'll set up a simple code that takes exactly Get's configuration and send it out so everyone can run it and see exactly what happens.

   Barry


> On Dec 1, 2021, at 8:00 PM, Abhyankar, Shrirang G via petsc-dev <petsc-dev at mcs.anl.gov> wrote:
> 
>  
>  
> From: Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>>
> Date: Wednesday, December 1, 2021 at 5:57 PM
> To: "Brown, Jedediah A (VISIT)" <jed at jedbrown.org <mailto:jed at jedbrown.org>>
> Cc: "Abhyankar, Shrirang G" <shrirang.abhyankar at pnnl.gov <mailto:shrirang.abhyankar at pnnl.gov>>, PETSc Development <petsc-dev at mcs.anl.gov <mailto:petsc-dev at mcs.anl.gov>>, Getnet Betrie <gbetrie at anl.gov <mailto:gbetrie at anl.gov>>
> Subject: Re: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?
>  
> Check twice before you click! This email originated from outside PNNL.
>  
> On Wed, Dec 1, 2021 at 6:55 PM Jed Brown <jed at jedbrown.org <mailto:jed at jedbrown.org>> wrote:
>> Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>> writes:
>> 
>> > On Wed, Dec 1, 2021 at 5:17 PM Abhyankar, Shrirang G <
>> > shrirang.abhyankar at pnnl.gov <mailto:shrirang.abhyankar at pnnl.gov>> wrote:
>> >
>> >> “You can certainly have many fields on a given edge, but I don't know
>> >> what it would mean to have two edges since no topological query could tell
>> >> the difference.”
>> >>
>> >>
>> >>
>> >> The two edges in a power grid represent two parallel power lines that are
>> >> connected between two locations (vertices). There are line ids (stored in
>> >> the component data) to distinguish the two lines.
>> >>
>> >
>> > Yes, so you can tell the difference in the function space (since difference
>> > current passes down each one), but _topologically_ you cannot. If you put
>> > duplicate cells in, then
>> > some topological queries will give unexpected results, like the join of the
>> > two vertices.
>> 
>> This could be modeled with some ghost vertices. So instead of
>> 
>>   a ------ b
>>    \_____/
>> 
>> you would set up
>> 
>>   a ---o---- b
>>    \___o___/
>> 
>> Those ghost vertices don't have to "do" anything, but they make the edges topologically distinct.
>> 
>> Shri, what problems might this cause?
> 
>  
> I don’t understand the figure you’ve drawn above. Sorry.
>  
> As a user, would I need to add anything to the way I am setting up the network/plex or any additional equations in the residual evaluation?
>  
> I do not have any issue right now for the power grid problem since I don’t require DMNetwork or DMPLEX to do the topological distinction between parallel edges. There are unique edge identifiers in my dataset through which I can make this distinction.
>  
>  
> Yes, this would work, but it looks like the multiple cells are not causing them problems right now with the questions they are asking the mesh.
>  
>    Matt
>  
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
>  
> https://www.cse.buffalo.edu/~knepley/ <https://gcc02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.cse.buffalo.edu%2F~knepley%2F&data=04%7C01%7Cshrirang.abhyankar%40pnnl.gov%7Cbcbb40fc51f6428ac17708d9b5264361%7Cd6faa5f90ae240338c0130048a38deeb%7C0%7C0%7C637739998211230005%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=Sg7eEbjzkSqVd6Sjg8IpTN3iXxMAvih0UNV0fkolO8w%3D&reserved=0>
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