Hi K,

heterogeneously_constrain_element_matrix_and_vector is not relevant to 
Reduced Basis stuff. For Reduced Basis formulations, you have to 
transform the problem using a lifting function so that it has zero 
Dirichlet BC's --- this is essential since you want your Reduced Basis 
space to be a vector space, i.e. it must contain 0 (which would be not 
be the case with non-zero Dirichlet BCs). This lifting function approach 
is what you described in your email already, so that's fine.

Once you've transformed your problem using a lifting function, then you 
just proceed as normal, e.g. as in reduced_basis_ex1. The only trick is 
you have to add your lifting function back on at the end to recover u 
from u'.

David



On 01/24/2013 11:10 PM, Kyunghoon Lee wrote:
> Hi all,
>
> In my previous email regarding inhomogeneous Dirichlet boundary conditions,
> David suggested using heterogenously_constrain_element_matrix_and_vector in
> introduction_ex4, but I'm not sure of how to deal with inhomogeneous
> Dirichlet BCs in connection with reduced basis models.  Suppose we have a
> simple steady state heat conduction model whose BCs are u = T on \Gamma and
> u = 0 on the rest surfaces.  After variable change, we solve
>
> a(u',v) = f(v) - a(u0,v)
>
> where 1) u' = u - T on \Gamma and u' = u on the rest surfaces; and 2) u0 =
> T on \Gamma and u0 = zero on the rest surfaces.  I thought we build the LHS
> then call attach_F_assembly to attach it, but in that case, I'm not sure
> how heterogenously_constrain_element_matrix_and_vector can be used.  Or
> should we attach a(u',v) and f(v) as usual then call
> heterogenously_constrain_element_matrix_and_vector to impose - a(u0,v) on
> the LHS?  I'd appreciate if someone can briefly describe how the function
> work.
>
> Regards,
> K. Lee.
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