[petsc-dev] Problem with unnamed side sets in DMPlexCreateExodus

[David Andrs]

Hi Matt!

On Jun 26, 2022, at 10:39, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Sun, Jun 26, 2022 at 8:31 AM David Andrs <andrsd at gmail.com <mailto:andrsd at gmail.com>> wrote:
> Hi Jed!
> 
> I have been thinking about this and I think more correct would be not to create the label with an empty name. It is not all or nothing kind of a deal. Some side sets may have a name, some may not.
> 
> What I sent is probably more convenient, since after loading the mesh there is either a label with a name or with an ID which can be easily grabbed and passed into `PetscDSAddBoundary`. However, I agree that assigning the name with an ID like this is specific to an application.
> 
> I can send a patch that will prevent the creation of a label with an empty name if you think this is what should be happening instead.
> 
> I think what Jed is suggesting is to use "Face Sets" if the name is empty. I currently prefer this solution.

I am not sure I follow. The “Face Sets” label gets created correctly in both cases as far as I can tell. 

If there is an unnamed side set in the Exodus file, then a new label gets created with no name. This label then contains all the unnamed side sets. That does not seem correct to me and that’s what I was suggesting to fix in case y'all also think that is not right.

> Would this screw up your current workflow?

No, it has no effect on my workflow.  Jed’s question made me realize that I need to create the labels with IDs as their names every time. In ExodusII, IDs are mandatory, names are not. We do not know upfront if the user would use an ID or a name, so I need to have both if they are present in the mesh file. But, that is as I said, specific to my application.

—
David

> 
> I would also like to have a consistent policy for everything, but it is hard for me to see what this would be right now.
> 
>   Thanks,
> 
>       Matt
>  
> —
> David
> 
> 
> > On Jun 25, 2022, at 22:54, Jed Brown <jed at jedbrown.org <mailto:jed at jedbrown.org>> wrote:
> > 
> > Do you think this is more correct than just using "Face Sets", which gives you a numbered index?
> > 
> > There is curently some inconsistency between file formats in whether various sets show up as stand-alone labels or values under Face Sets. And there's this lingering issue to have a way to name Face Sets (and Cell Sets).
> > 
> > https://gitlab.com/petsc/petsc/-/issues/689 <https://gitlab.com/petsc/petsc/-/issues/689>
> > 
> > The issue is that if we just make named labels, there's no good way to do structured traversal (handle all Face Sets) and one also has to be careful to avoid namespace collisions between application sets and sets created by the mesh.
> > 
> > David Andrs <andrsd at gmail.com <mailto:andrsd at gmail.com>> writes:
> > 
> >> Hello!
> >> 
> >> The current behavior in DMPlexCreateExodus is assuming that side sets are always named. However, that is not always true. If there are unnamed side sets in an ExodusII file, the created DM will contain a label with an empty name (“”) with as many stratas as there are side sets. See the sample output from DMView below:
> >> 
> >> Labels:
> >>  celltype: 3 strata with value/size (0 (138900), 4 (125514), 1 (265620))
> >>  depth: 3 strata with value/size (0 (138900), 1 (265620), 2 (125514))
> >>  Cell Sets: 4 strata with value/size (1 (57888), 2 (57888), 4 (1824), 5 (7914))
> >>  Face Sets: 6 strata with value/size (1000 (28944), 1001 (28944), 1003 (28944), 1005 (15144), 1100 (120), 1200 (120))
> >>  : 6 strata with value/size (1000 (28944), 1001 (28944), 1003 (28944), 1005 (15144), 1100 (120), 1200 (120))
> >> 
> >> The attached patch fixes the behavior and names the side sets according to their IDs if there is no name associated with it in the ExodusII file. See the modified behavior below:
> >> 
> >> Labels:
> >>  celltype: 3 strata with value/size (0 (138900), 4 (125514), 1 (265620))
> >>  depth: 3 strata with value/size (0 (138900), 1 (265620), 2 (125514))
> >>  Cell Sets: 4 strata with value/size (1 (57888), 2 (57888), 4 (1824), 5 (7914))
> >>  Face Sets: 6 strata with value/size (1000 (28944), 1001 (28944), 1003 (28944), 1005 (15144), 1100 (120), 1200 (120))
> >>  1000: 1 strata with value/size (1000 (28944))
> >>  1001: 1 strata with value/size (1001 (28944))
> >>  1003: 1 strata with value/size (1003 (28944))
> >>  1005: 1 strata with value/size (1005 (15144))
> >>  1100: 1 strata with value/size (1100 (120))
> >>  1200: 1 strata with value/size (1200 (120))
> >> 
> >> The patch is against 3.17.0, but is seems it should apply cleanly on 3.17.2.
> >> 
> >> With regards,
> >> 
> >> David Andrs
> 
> 
> 
> -- 
> 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/ <http://www.cse.buffalo.edu/~knepley/>
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