Merge pull request libMesh#231 from libMesh/dirichlet_nan

Dirichlet nan

include/base/dirichlet_boundaries.h

@@ -40,6 +40,25 @@
 namespace libMesh
 {
 
+// ------------------------------------------------------------
+// DirichletBoundary class definition
+
+/**
+ * This class allows one to associate dirichlet boundary values with
+ * a given set of mesh boundary ids and system variable ids.
+ *
+ * Dirichlet values must be supplied as the input function "f"; when
+ * using some specialized elements, gradient values must be supplied
+ * via the input function "g".
+ *
+ * Dirichlet functions are allowed to return NaN; if this is
+ * encountered, then the degree of freedom values in a patch around
+ * the location of the returned NaN will be left unconstrained.  E.g.
+ * a NaN on a boundary edge in 3D would leave that edge and the two
+ * adjoining face interiors unconstrained, but would still permit the
+ * other edge and node DoFs around those faces to be constrained.
+ */
+
 class DirichletBoundary
 {
 public:

src/base/dof_map_constraints.C

@@ -831,7 +831,7 @@ private:
           for (unsigned int i = 0; i < n_dofs; i++)
             {
               DofConstraintRow empty_row;
-              if (dof_is_fixed[i])
+              if (dof_is_fixed[i] && !std::isnan(Ue(i)))
                 add_fn (dof_indices[i], empty_row, Ue(i));
             }
         }