dolfin team mailing list archive

[kent-and@xxxxxxxxx]

> Thanks Garth,
>
> On Jul 15, 2009, at 10:44 AM, Garth N. Wells wrote:
>
>>
>>
>> mspieg wrote:
>>> Hi All,
>>>    I think there is a bug when trying to read a MeshFunction from
>>> a file that was generated on a SubMesh.  I've attached some python
>>> based on the SubMesh demo, that demonstrates the problem.  I think
>>> the issue is that there is an extra MeshFunction embedded in a
>>> SubMesh to describe the "global vertex indices" that gets read
>>> instead of the intended mesh-function.
>>
>> It might be a while before anyone gets to this. We hope to have a
>> new, simple to use bug tracking system (i.e. not Bugzilla) in place
>> soon to keep track of these types of issues, especially since they
>> tend to be forgotten while everyone is on holiday.
>>
>
> That would be good.  I can work around this easily enough at the
> moment (if I just strip out the unwanted MeshFunction from the file
> everything works fine).  If I don't see a fix, I'll post something on
> the new bug tracking system when it's in place.
>>
>>> On a related note, it's easy enough to extract a SubMesh from a
>>> larger Mesh using a MeshFunction, but what is the best way to
>>> extract just the piece of a discrete function on the SubMesh, when
>>> the Function is originally defined for a Function Space on the
>>> larger mesh. (does this make sense?)
>>> These issues arise from a multiphysics problem that I'm working
>>> with overlapping domains  where I basically want to solve an
>>> embedded porous media problem on a subdomain of a larger stokes
>>> flow (this is slightly different from the fluid-structure demo
>>> where the two domains only share a boundary.)
>>
>> Kent has been working on something like this. Have you looked at
>>
>>   demo/function/restriction
>
> I started to look at this...A couple of questions/issues
>




Sorry for not getting back on you before now.



> 1) at the moment restriction only takes MeshFunction<bool> whereas
> SubMesh takes (MeshFunction<uint>,uint) which allows multiple
> subdomains.  It might be nice if these two had similar interfaces
> particularly since I think it makes more sense to use SubMesh to
> apply boundary conditions on the subdomain.

Agree, I'll do this.

>
> 2) At the moment restriction seems to mainly apply to the function
> space, not the function (i.e. the demo just creates a new function on
> the restricted function space, not extracts a restricted function
> from the larger space).  I suspect this wouldn't be too hard to do,
> but it's not entirely obvious what the best way to do this would
> be...a nice interface would be similar to FunctionSpace.restriction
> ()  something like F=Function(V), F_restricted=F.restriction
> (MeshFunction<?>)

Something like this can be done, I agree. At least the mapping between
the restricted and the full space should be exposed such that this is
possible.

>
> 3) I have no idea how to handle this in parallel (but a lot of these
> issues are related to local<->global mappings and maybe something can
> be cleanly designed for all of these problems)

I have no idea either :)

>
> Like I said, I can work around all of this at the moment, but it
> would be useful to think through the best way to deal with these
> sorts of embedded multi-physics problems.
>
> Thanks again
> marc
>
>

Agree

Kent


>>
>> ?
>>
>> Garth
>>
>>> All help greatly appreciated as always
>>> cheers
>>> marc
>>> p.s. all current dev repositories
>>> p.p.s. another official release would be great...a lot has changed
>>> since 2009-04
>>> ---------------------------------------------------------------------
>>> ---
>>> ----------------------------------------------------
>>> Marc Spiegelman
>>> Lamont-Doherty Earth Observatory
>>> Dept. of Applied Physics/Applied Math
>>> Columbia University
>>> http://www.ldeo.columbia.edu/~mspieg
>>> tel: 845 704 2323 (SkypeIn)
>>> ----------------------------------------------------
>>> ---------------------------------------------------------------------
>>> ---
>>> _______________________________________________
>>> DOLFIN-dev mailing list
>>> DOLFIN-dev@xxxxxxxxxx
>>> http://www.fenics.org/mailman/listinfo/dolfin-dev
>
> ----------------------------------------------------
> Marc Spiegelman
> Lamont-Doherty Earth Observatory
> Dept. of Applied Physics/Applied Math
> Columbia University
> http://www.ldeo.columbia.edu/~mspieg
> tel: 845 704 2323 (SkypeIn)
> ----------------------------------------------------
>
>
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