dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Aug 19, 2008 at 01:49:22PM +0200, Jed Brown wrote:
> On Tue 2008-08-19 13:40, Anders Logg wrote:
> > On Tue, Aug 19, 2008 at 12:12:50PM +0200, Jed Brown wrote:
> > > On Tue 2008-08-19 11:59, Anders Logg wrote:
> > > > On Thu, Aug 14, 2008 at 10:10:03PM +0000, Jed Brown wrote:
> > > > > One way to implement this is to allocate a vector for Dirichlet values,
> > > > > a vector for Homogeneous values, and a Combined vector.  The Homogeneous
> > > > > vector is the only one that is externally visible.
> > > > 
> > > > Isn't this problematic? I want the entire vector visible externally
> > > > (and not the homogeneous part). It would make it difficult to plot
> > > > solutions, saving to file etc.
> > > > 
> > > > Maybe the Function class could handle the wrapping but it would involve a
> > > > complication.
> > > 
> > > Right, by `externally visible' I mean to the solution process, that is
> > > time-stepping, nonlinear solver, linear solvers, preconditioners.  The
> > > vector you are concerned about is the post-processed state which you can
> > > get with zero communication.  It is inherently tied to the mesh and
> > > anything you do with it likely needs to know mesh connectivity.  I don't
> > > think it is advantageous to lump this in with the global state vector.
> > > 
> > > Jed
> > 
> > I don't understand. What is the global state vector?
> 
> The global state vector is the vector that the solution process sees.
> Every entry in this vector is a real degree of freedom (Dirichlet
> conditions have been removed).  This is the vector used for computing
> norms, applying matrices, etc.  When writing a state to a file, this
> global vector is scattered to a local vector and boundary conditions are
> also scattered into the local vector.  The local vector is serialized
> according to ownership of the mesh (you have to do this anyway).
> 
> Jed

I'm only worried about how to create a simple interface. Now, one may
do

  u = Function(...);
  A = assemble(a, mesh)
  b = assemble(L, mesh)
  bc.apply(A, b)
  solve(A, u.x(), b)
  plot(u)

How would this look if we were to separate out Dirichlet dofs?

-- 
Anders

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