On Nov 17, 2010, at 3:09 PM, Roy Stogner wrote: > > > On Wed, 17 Nov 2010, Cody Permann wrote: > >> On Nov 17, 2010, at 2:24 PM, Roy Stogner wrote: >> >>> And because >>> PointLocatorTree only operates on active elements, it shouldn't care >>> whether or not we delete subactive elements after it's constructed. >> >> Sounds good, but are you completely sure? Check out the find_element() >> routine >> on line 501 inside of tree_node.C which is where the seg fault occurs. That >> method >> is using an internal data structure of pointers to elements. That data >> structure would >> be out of date after the call to mesh::contract() because contract() calls >> renumber_nodes_and_elements() which changes pointers around. > > I don't think it's supposed to change pointers around (other than by > deleting the subactive elements and unused nodes), at least in the > existing Mesh implementations. ParallelMesh uses a mapvector<Elem*> > as a container; SerialMesh uses a vector<Elem*>. We move Elem* from > place to place within at least the latter data structure, but the Elem > itself should never change addresses.
OK fair enough. Here is my latest observation. I would assume that the calls to coarsen_elements() and refine_elements() in EquationSystems::reinit() would both return false having just completed the refine_and_coarsen_elements() routine right before hand. However this is not the case. There are additional elements coarsened or refined in the reinit() routine - further changing the mesh and invalidating the point_locator... > >> I propose we add a call to clear_point_locator() right after the >> call to contract() inside of EquationSystems.reinit(). I already >> made this change in my local copy and everything seems to be working >> correctly without the explicit call to clear the point locator in >> user code anymore. > > Sounds like the best place for an additional clear_point_locator() is > at the end of UnstructuredMesh::contract(), then. That method is > supposed to be callable in more contexts, even if we never do so and I > doubt any of our users do either. > > Once that's done, your patch is probably safe to commit - I still want > to better understand this bug but it appears we've at least fixed it. > --- > Roy ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev _______________________________________________ Libmesh-devel mailing list Libmesh-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-devel
