]> https://gitweb.dealii.org/ - dealii.git/commitdiff
Add one more paragraph.
authorWolfgang Bangerth <bangerth@math.tamu.edu>
Thu, 14 Apr 2011 13:34:07 +0000 (13:34 +0000)
committerWolfgang Bangerth <bangerth@math.tamu.edu>
Thu, 14 Apr 2011 13:34:07 +0000 (13:34 +0000)
git-svn-id: https://svn.dealii.org/trunk@23595 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/examples/step-46/doc/intro.dox

index b3bd8450c105880c03e6887f644ad3d15cb2f363..a9f9eb426baceb3ea4b31ca524c77ddf5628048c 100644 (file)
@@ -377,6 +377,17 @@ solid cell is refined, yielding the following code:
                }
            }
 @endcode
+
+The call <code>constraints.add_line(t)</code> tells the
+ConstraintMatrix to start a new constraint for degree of freedom
+<code>t</code> of the form $x_t=\sum_{l=0}^{N-1} c_{tl} x_l +
+b_t$. Typically, one would then proceed to set individual coefficients
+$c_{tl}$ to nonzero values (using ConstraintMatrix::add_entry) or set
+$b_t$ to something nonzero (using
+ConstraintMatrix::set_inhomogeneity); doing nothing as above, funny as
+it looks, simply leaves the constraint to be $x_t=0$, which is exactly
+what we need in the current context.
+
 Note that there are cases where this may yield incorrect results:
 notably, once we find a solid neighbor child to a current fluid cell,
 we assume that all neighbor children on the common face are in the

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