[firedrake] Boundary conditions

[David Ham]

mymatrix = assemble(myform, bcs=bcs)

mymatrix.assemble() # Force the delayed assembly.

mymatrix.M.values # Numpy array.



On 2 February 2014 09:04, Cotter, Colin J <colin.cotter at imperial.ac.uk>wrote:

>  OK, next question is whether I can output a numpy matrix for a bilinear
> form assembled with boundary conditions, i.e. whether I can get the reduced
> matrix with the boundary rows and columns removed?
>
> I can see that the bcs are postponed until the solve, so if this exists it
> would just be a utility for testing. If it doesn't I can remove them myself.
>
> --cjc
>  ------------------------------
> *From:* firedrake-bounces at imperial.ac.uk [firedrake-bounces at imperial.ac.uk]
> on behalf of Cotter, Colin J [colin.cotter at imperial.ac.uk]
> *Sent:* 02 February 2014 08:54
>
> *To:* firedrake
> *Subject:* Re: [firedrake] Boundary conditions
>
>   Ah good, works, thanks.
>
> --cjc
>  ------------------------------
> *From:* firedrake-bounces at imperial.ac.uk [firedrake-bounces at imperial.ac.uk]
> on behalf of David Ham [David.Ham at imperial.ac.uk]
> *Sent:* 01 February 2014 22:12
> *To:* firedrake
> *Subject:* Re: [firedrake] Boundary conditions
>
>  Standard GMSH problem: if you have a physical line you also need a
> physical surface or GMSH will drop all the interior elements from the
> output.
>
> On Saturday, February 1, 2014, Cotter, Colin J <
> colin.cotter at imperial.ac.uk> wrote:
>
>>  Dear Firedrakers,
>>   I decided to create another set of cohomology tests, this time with
>> Dirichlet boundary conditions, since there is a nice result relating the
>> kernels of the operators with and without Dirichlet boundary conditions
>> (for the maths-curious, it's Poincare duality).
>>
>>   However, I can't get the boundary tags into Firedrake from gmsh. If I
>> attempt to tag the boundary using "Physical Line" in gmsh (see bottom of
>> this email for the .geo file), the line
>> >>mesh = Mesh("annulus.msh")
>> produces:
>> *** ERROR ***
>> Error message: Unsupported mixture of face/element types
>>
>> Removing the physical line makes the error message go away, so there is
>> something wrong with that line.
>>
>> What have I done wrong?
>>
>> all the best
>> --Colin
>>
>> Point(1) = {0, 0, 0, 1.0};
>> Point(2) = {1, 0, 0, 1.0};
>> Point(3) = {1, 1, 0, 1.0};
>> Point(4) = {0, 1, 0, 1.0};
>> Point(5) = {0.3333333333333, 0.3333333333333, 0, 1.0};
>> Point(6) = {0.66666666666666, 0.3333333333333, 0, 1.0};
>> Point(7) = {0.66666666666666, 0.66666666666666, 0, 1.0};
>> Point(8) = {0.3333333333333, 0.66666666666666, 0, 1.0};
>> Line(1) = {1, 2};
>> Line(2) = {2, 3};
>> Line(3) = {3, 4};
>> Line(4) = {4, 1};
>> Line(5) = {5, 6};
>> Line(6) = {6, 7};
>> Line(7) = {7, 8};
>> Line(8) = {8, 5};
>> Line Loop(1) = {1, 2, 3, 4};
>> Line Loop(2) = {5, 6, 7, 8};
>> Plane Surface(1) = {1,2};
>> Physical Line(9) = {2, 3, 4, 1, 6, 7, 8, 5};
>>
>>
>
> --
> Dr David Ham
> Departments of Mathematics and Computing
> Imperial College London
>
> http://www.imperial.ac.uk/people/david.ham
>
>


-- 
Dr David Ham
Departments of Mathematics and Computing
Imperial College London

http://www.imperial.ac.uk/people/david.ham
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