dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Fri, Jun 06, 2008 at 10:28:54AM +0200, Anne Voigt wrote:
> 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                                                    

Works for me. Take a look in

  sandbox/misc/

Does this give you a segmentation fault?

-- 
Anders

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