On Wed, 16 Apr 2008, John Peterson wrote: > Just out of curiosity, what would be the "right thing" to do in order > to compare two meshes with different (still nested) refinement > patterns or two solutions on completely non-nested grids?
Loop over one grid. On each element, if the other grid is coarser, you integrate here. If the other grid is finer, you get the corresponding ancestor element there and integrate on all its active descendants. That way you get the numerical integration right up to floating point error, without worrying about quadrature error. > It's not immediately obvious to me what such a comparison would > actually tell you in any case... Oh, well I just meant that *what* to do to integrate between two such grids was obvious; *why* to do such a comparison isn't obvious to me either. If you're contrasting two different refinement strategies then you generally want to compare them to a completely finer reference solution, not to each other. I bet you'd usually still get a good error indicator for grid A in the places where grid B was more refined, and vice versa; running into pollution effects would be a nightmare, though. It's also debatably a good idea to use that sort of "integrate whichever mesh is locally finer" code when you're integrating to assemble a system rather than to take a norm. Back when I was playing with deal.II some of my experiments were to solve multiphysics problems on independently refined nested grids. You can save a lot of degrees of freedom that way if you've got a system that's loosely coupled enough to handle it. --- Roy ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
