Hi Roy, From you definition of *hierarchich*, SZABAB would classify as one, correct? The polynomials are nest. My experience with HIERARCHIC has been unfavorable, with convergence issues of iterative solvers. I have not seen any such problems with SZABAB, and BERNSTEIN, so am favoring those.
I managed to get the higher order SZABAB working with three modifications: -- modified FEInterface::extra_hanging_dofs() to be true for SZABAB. -- FEInterface::compute_constraints() does not do anything for SZABAB. Added a case SZABAB: for that. -- fe_szabab.C needs FE<2, SZABAB>::compute_constraints. With this, h-refinement of higher order SZABAB works without problems. I am not sure if this is the issue plaguing hp-refinement, but I will get to it soon. -Manav On Thu, Dec 5, 2013 at 2:58 PM, Roy Stogner <[email protected]>wrote: > > On Wed, 4 Dec 2013, Manav Bhatia wrote: > > — 2nd order LAGRANGE FE type, *with h-refinemement* works fine and >> converges. >> > > This is as I'd expect - the current libMesh adaptive p-refinement code > assumes a hierarchic basis and should fail in weird ways (or in devel > mode, throw an error) without one. > > > — Changing FE type to SZABAB and *using h-refinement* leads to >> unrealistic (huge) residual values immediately after first >> h-refinement and the plotted solution has odd looking spikes in each >> element next to a hanging node. >> >> This seems to be an expected behavior given the bug described in the >> libmesh-devel thread you had sent to me. (?) >> > > No, actually. The bug I described should affect adaptive > hp-refinement, but not pure adaptive h-refinement. > > What p level and element type were you using that you saw a failure > with h-refinement? I don't know much about the SZABAB elements but > it looks like perhaps they require extra_hanging_dofs==true but aren't > getting that in fe_interface.C. > > > Out of the higher-order polynomials, SZABAB is nested, but BERNSTEIN >> is not since the whole basis changes as soon as the p-order is >> modified. Does this bug/discussion affect BERNSTEIN in the same was >> as it does SZABAB? >> > > With non-nested (what I called "hierarchic" before, not referring only > to the HIERARCHICs) polynomials we don't support p-refinement at all > yet. That's not so much a bug as an unimplemented feature. > --- > Roy ------------------------------------------------------------------------------ Sponsored by Intel(R) XDK Develop, test and display web and hybrid apps with a single code base. Download it for free now! http://pubads.g.doubleclick.net/gampad/clk?id=111408631&iu=/4140/ostg.clktrk _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
