Thanks you guys for all the help.

Dan

On Sat, Jul 21, 2012 at 5:35 PM, Wolfgang Bangerth
<[email protected]>wrote:

>
>  in short: it is a bit difficult right now. But I attached a version of
>>> step-40, that does what you want. Obviously I had to change the
>>> problem to a right hand side where I have the analytic solution. The
>>> main part of the code is:
>>>
>>>      Vector<double> cellwise_errors (triangulation.n_active_cells(**));
>>>
>>>      VectorTools::integrate_**difference (dof_handler,
>>>                                         locally_relevant_solution,
>>>                                         Coefficient<dim>(),
>>>                                         cellwise_errors,
>>>                                         quadr,
>>>                                         VectorTools::L2_norm);
>>>
>>>      unsigned int index = 0;
>>>      double my_value = 0;
>>>      typename DoFHandler<dim>::active_cell_**iterator
>>>        cell = dof_handler.begin_active(),
>>>        endc = dof_handler.end();
>>>      for (; cell!=endc; ++cell, ++index)
>>>        if (cell->is_locally_owned())
>>>            my_value += cellwise_errors(index)***cellwise_errors(index);
>>>
>>>      double err= std::sqrt(Utilities::MPI::sum(**my_value,
>>> MPI_COMM_WORLD));
>>>
>>
> integrate_difference already sets the output vector to zero and only fills
> entries that correspond to locally owned cells, so one can abbreviate this
> to simply do
>   double err
>     = std::sqrt(Utilities::MPI::sum(**cellwise_errors * cellwise_errors,
>                                     MPI_COMM_WORLD));
>
> But yes, let's see what can be done for the workshop!
>
> Best
>  W.
>
> --
> ------------------------------**------------------------------**
> ------------
> Wolfgang Bangerth               email:            [email protected]
>                                 www: 
> http://www.math.tamu.edu/~**bangerth/<http://www.math.tamu.edu/~bangerth/>
>
>
>
>
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