dolfin team mailing list archive

[Gerd Wachsmuth <gerd.wachsmuth@xxxxxxxxxxxxxxxxxxxxxxxxx>]

On Thu, 21 Oct 2010, Anders Logg wrote:

> Gerd Wachsmuth skrev 2010-10-21 12.58:
>> On Wed, 20 Oct 2010, Anders Logg wrote:
>>> Marie Rognes skrev 2010-10-14 12.28:
>>>> On 14. okt. 2010 11:13, Gerd Wachsmuth wrote:
>>>>> This works fine in 2D. But in 3D, extrapolation is not implemented.
>>>>>
>>>>>
>>>>
>>>> Ah.
>>>>
>>>
>>> The problem is that this functionality is missing in CGAL so we have to
>>> implement it ourselves and no one has done that yet.
>>>
>>
>> In my opinion the problem is that Dolfin want to evaluate the function at
>> points which does not belong to the integration domain - or at points
>> lying to close at the boundary.
>>
>> In my example the function w is defined only on a subdomain. Hence there
>> should be no error if this function is integrated over this subdomain.
>> By extrapolating this bug is only covered up.
>
> Have you checked which point is thought to be outside of the domain?
> Perhaps it's a small round-off error that causes the problem?
>

Yep. The problem seems to occur at points lying on the boundary.

-- 
Assembling over subdomain fails
https://bugs.launchpad.net/bugs/660334
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Status in DOLFIN: New

Bug description:
Following setup:

I have a mesh (with FunctionSpace V) and a submesh (with FunctionSpace W). Assembling a linear form on V over this subdomain involving a coefficient from W will fail.

I think the problem is that Dolfin would like to evaluate the function from W at the boundary of the subdomain. Maybe due to rounding errors this point lies outside the subdomain and the evaluation fails.

It does not happen, if W is a CG or DG space.