[aspect-devel] VectorTools::integrate_difference fails to return an error that decreases under grid refinement

Wolfgang Bangerth bangerth at tamu.edu
Wed Oct 26 06:35:46 PDT 2016

On 10/25/2016 02:17 PM, Elbridge Gerry Puckett wrote:
> We'd be grateful for any help you can give us, since we've been struggling
> with this issue for about a month now.

The usual situation where this happens is if the implementation of the "exact 
solution" is wrong, i.e., you want to compute
   || u_h - u ||
but instead you compute
   || u_h - v ||
with some v that has nothing to do with u and consequently the norm does not 
converge to zero.

I don't quite understand where in your code you set the exact solution. But 
that's where I would check -- maybe you have a sign error, of a missing factor.


Wolfgang Bangerth          email:                 bangerth at colostate.edu
                            www: http://www.math.colostate.edu/~bangerth/

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