On Thu, 9 Feb 2017, Rossi, Simone wrote:
> Additionally I noticed something wrong in the assembly. > When I use LAGRANGE fefamily my global rhs vector (for a 2D elasticity > problem) looks like this > > u_x_point0 > u_y_point0 > > u_x_point1 > u_y_point1 > > . > . > . > > u_x_pointN > u_y_pointN > > and the local vector is organized in the following manner > > u_x_point0 > u_x_point1 > u_x_point2 > > u_y_point0 > u_y_point1 > u_y_point2 DoF ordering isn't "right" or "wrong", it's a design decision. With libMesh the local vector ordering is fixed (that's what lets us use DenseSubMatrix which has only an offset and not a stride to worry about); the global vector ordering should be either (processor, node, variable) or (processor, variable, node) depending on whether you use --node_major_dofs or not. > Does this still happen with other fefamilies? With more interesting FE types, and adaptive p refinement, and adaptive h refinement with hanging nodes (which may conjoin vertex with side/edge degrees of freedom or may only couple them via constraint equations, depending on FE type), global DoF ordering can do much more complicated things, and trying to second-guess it at the application level will just leave you with incompatibilities at best or bugs at worst. Just use the local vectors, with submatrices and subvectors to index into them. > My routine for assembly of traction boundary conditions works with > LAGRANGE fefamily. For a 2D square with 2 elements Two elements, each with 4 degrees of freedom, but not actually sharing any nodes so that's you end up with 8 degrees of freedom in the full system? But then you'd have 6 degrees of freedom with MONOMIAL or 8 with L2_LAGRANGE elements, not 12. I need more detailed description here. --- Roy ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
