dolfin team mailing list archive

[Anne Voigt <anne.voigt@xxxxxxxxxxxxxxxxxxxxx>]

Am Dienstag, den 03.06.2008, 22:02 +0200 schrieb Anders Logg:
> On Fri, May 30, 2008 at 10:02:29AM +0200, Anne Voigt wrote:
> > Hello all,
> > 
> > I'm working with FFC for quite a while and I like the easy way to
handle
> > multilinear forms with the help of FFC.
> > 
> > But now I have a problem where I'm not sure if it is possible to
> > programme this with FFC.
> > 
> > I'm working on an optimal control problem where I have to solve an
> > integral over just a part of the whole twodimensional domain (x,y)
\in
> > \Omega. So what I need is the bilinear form
> > 
> > \int_{y_0}^{y_1} u*v dy where [y_0,y_1] \in \Omega
> > 
> > Is it possible to implement something like that in FFC and how can I
do
> > that?  
> > 
> > Hope somebody can help me?!
> 
> Yes, that's easy (but not so well documented I admit).
> 
> The simplest way is to just supply a SubDomain as argument to the
assembler:
> 
>   assemble(A, form, mesh, sub_domain);
> 
> Create a SubDomain which overloads the inside() function, returning
> True when you are inside your subdomain, for example
> 
>   class MySubDomain : public SubDomain
>   {
>     bool inside(const real* x, bool on_boundary) const
>     {
>       return x[0] + x[1] > 1.0;
>     }
>   };  
> 
> If you can't specify your domain based on an expression, you need to
> create a MeshFunction that labels which cells are included in your
> domain.
> 
> It's also possible to have different integrals over different
> subdomains, integrals over subsets of the boundary etc.
> 

Thanks for your respond. But it seems like it would not work.

If I do

#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>

#include <dolfin.h>
#include <dolfin/dolfin_mf.h>


#include "MassMatrix2D.h"

using namespace dolfin;
using namespace std;


class MySubDomain : public SubDomain
{
        bool inside(const dolfin::real *x, bool on_boundary) const
        {       
        return true;    
        }
};

int main(int argc, char* argv[])
{
  dolfin_init(argc, argv);
  Mesh mesh("cylinder_10.xml");

  int inode = mesh.numVertices();
  PETScMatrix K;
  MassMatrix2DBilinearForm a;
  MySubDomain subDomain;
  assemble(K, a, mesh, subDomain);
}

I get there error message

| Assembling over cells                                           |
|-----------------------------------------------------------------| 0.0%
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation,
probably memory access out of range
[0]PETSC ERROR: Try option -start_in_debugger or
-on_error_attach_debugger
[0]PETSC ERROR: or see
http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#Signal[0]PETSC ERROR: or try http://valgrind.org on linux or man libgmalloc on Apple to find memory corruption errors
[0]PETSC ERROR: likely location of problem given in stack below
[0]PETSC ERROR: ---------------------  Stack Frames
------------------------------------
[0]PETSC ERROR: Note: The EXACT line numbers in the stack are not
available,
[0]PETSC ERROR:       INSTEAD the line number of the start of the
function
[0]PETSC ERROR:       is given.
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Signal received!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 2.3.3, Patch 8, Fri Nov 16
17:03:40 CST 2007 HG revision:
414581156e67e55c761739b0deb119f7590d0f4b      
...

But I should get the same result as I would get if I woulde assemble
over the whole domain or???
It does also not work if would compile it with your little example. So
is it possible that there is a bug in one of the functions?!

Anne