Hi W,

You are right. I am not bounded by the memory at this moment. The only 
potential issue I can think of at this stage is the computation of the 
error norm. Technically, if I feed the slots in global RHS corresponding to 
bubble support as zero, the solution at the bubble support should zero. 
Then the error norm would be the same as compared to use solutions at 
vertices only. Is this presumption valid here?

Regards,
Lixing

On Friday, January 8, 2021 at 12:40:54 PM UTC+8 Wolfgang Bangerth wrote:

> On 1/7/21 6:58 PM, Lixing Zhu wrote:
> > 
> > I implemented the local elimination as you suggested and it works. 
> However, 
> > this ends up with many extra "redundant" DOFs in the global system. For 
> > example, if I am using N*N linear elements for a scalar 2D problem with 
> > structured mesh, instead of (N+1)^2 global DOFs, I end up with (N+1)^2 + 
> N^2 
> > global DOFs. The extra DOFs are coming from the bubble supports. Of 
> course, 
> > they won't affect the solution at vertices due to the nature of bubble 
> > functions, but such an increase of DOFs may require more memory in the 
> > solution process. How should I also reduce the size of the global system?
>
> Do you need to? Is memory consumption an issue for you? Unless you have a 
> concrete problem, it's probably not worth optimizing for.
>
> Best
> W.
>
> -- 
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> www: http://www.math.colostate.edu/~bangerth/
>
>

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