This may not be what you want to do, IMHO. In the extreme case: If you compute the Uexact vector and then do the vec*mat*vec, then you'll get a result of 0 for problems where your method gives you an interpolant of the exact solution, even if that interpolant doesn't equal the exact solution.
If you evaluate the energy norm quadrature point by quadrature point, you'll get a more accurate estimate of the error in general and you can easily test for quadrature error by bumping up the order of your rule. --- Roy On Tue, 19 Jan 2016, David Knezevic wrote: > Assemble the Uexact vector, then compute the difference e = U - Uexact. > > You can also refer to error_estimation/exact_solution.h, but I believe > that's used for computing L2 or H1 error, not an arbitrary energy norm. > > David > > > > On Tue, Jan 19, 2016 at 5:04 PM, Junchao Zhang <junchao.zh...@gmail.com> > wrote: > >> How to get e = U - Uex? Is there a libmesh interface for that? >> >> --Junchao Zhang >> >> On Tue, Jan 19, 2016 at 3:57 PM, David Knezevic < >> david.kneze...@akselos.com> wrote: >> >>> Assuming you've already assembled K, so you can just do a matvec >>> (SparseMatrix::vector_mult) followed by a dot product (NumericVector::dot). >>> >>> David >>> >>> >>> >>> On Tue, Jan 19, 2016 at 4:53 PM, Junchao Zhang <junchao.zh...@gmail.com> >>> wrote: >>> >>>> Hello, >>>> I want to compute e^TKe as a measure of the error of a solution. Here >>>> e = >>>> U - Uex, supposing I know the analytic answer to the PDE. >>>> How can I do it in libmesh? Is there an example? >>>> Thank you. >>>> >>>> --Junchao Zhang >>>> >>>> ------------------------------------------------------------------------------ >>>> Site24x7 APM Insight: Get Deep Visibility into Application Performance >>>> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month >>>> Monitor end-to-end web transactions and take corrective actions now >>>> Troubleshoot faster and improve end-user experience. Signup Now! >>>> http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 >>>> _______________________________________________ >>>> Libmesh-users mailing list >>>> Libmesh-users@lists.sourceforge.net >>>> https://lists.sourceforge.net/lists/listinfo/libmesh-users >>>> >>> >>> >> > ------------------------------------------------------------------------------ > Site24x7 APM Insight: Get Deep Visibility into Application Performance > APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month > Monitor end-to-end web transactions and take corrective actions now > Troubleshoot faster and improve end-user experience. Signup Now! > http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 > _______________________________________________ > Libmesh-users mailing list > Libmesh-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/libmesh-users > > ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
