dolfin team mailing list archive

[Murtazo Nazarov <murtazo@xxxxxxxxxxx>]

Anders Logg wrote:
> On Mon, Mar 31, 2008 at 07:15:23PM +0200, Murtazo Nazarov wrote:
>   
> > Anders Logg wrote:
> >     
> > > On Mon, Mar 31, 2008 at 03:52:57PM +0200, Murtazo Nazarov wrote:
> > >   
> > >       
> > > > Hi,
> > > >
> > > > I want to apply a boundary condition to the vertices on a boundary. For that I define:
> > > >
> > > > // Sub domain for MyBC                                                                             
> > > > class MyBC_Boundary2D : public SubDomain
> > > > {
> > > > public:
> > > >   bool inside(const real* p, bool on_boundary) const
> > > >   {
> > > >     return  on_boundary && (p[0] < xmax - bmarg) && (p[0] > xmin + bmarg);
> > > >   }
> > > > };
> > > >
> > > > Then I initialize:
> > > > //-----------------------------------------------------------------------------                      
> > > > void MyBC::init(SubDomain& sub_domain)
> > > > { ...
> > > >   mesh.init(0);
> > > >   sub_domains = new MeshFunction<uint>(mesh, 0);
> > > > ...}
> > > >     
> > > >         
> > > Do you remember to set everything to 1 (number of subdomains) here?
> > >
> > >   
> > >       
> > Yes I do:
> >
> >   // Mark everything as sub domain 
> > 1                                                                
> >   (*sub_domains) = 1;
> >
> >
> >   // Mark the sub domain as sub domain 
> > 0                                                            
> >   sub_domain.mark(*sub_domains, 0);
> >
> > /murtazo
> >     
>
> Then I have no idea. You just need to dig into the code and see what
> goes wrong.
>
>   
I think I found a mistake in Subdomain.mark(). The thing is bool 
on_boundary should be defined
inside the loop for computing subdomain marker:

 // Always false when not marking 
facets                                                                                    

 //bool on_boundary = 
false;                                                                                                


 // Compute sub domain 
markers                                                                                              

 for (MeshEntityIterator entity(mesh, dim); !entity.end(); ++entity)
 {
   bool on_boundary = false;
   ...
  }

Otherwise, if you want to apply a boundary condition on vertices, it 
becomes always
true after once meeting a vertex on the boundary.


It solved problem for me.

/murtazo