Merge pull request #16036 from bangerth/affine-17

dealii · Sep 22, 2023 · d6cf33b · d6cf33b
2 parents 16bd9a9 + 9e8b515
commit d6cf33b
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diff --git a/doc/doxygen/headers/constraints.h b/doc/doxygen/headers/constraints.h
@@ -443,10 +443,7 @@
  * @f[
  *   (C^T A C + Id_c) \tilde x = C^T (b - A\,k)
  * @f]
- * instead [1] (M. S. Shephard. Linear multipoint constraints applied via
- * transformation as part of a direct stiffness assembly process.
- * <i>International Journal for Numerical Methods in Engineering</i>
- * 20(11):2107-2112, 1985).
+ * instead (see, for example, @cite Shephard1984).
  *
  * Here, $A$ is a given (unconstrained) system matrix for which we only
  * assume that we can apply it to a vector but can not necessarily access

diff --git a/doc/doxygen/references.bib b/doc/doxygen/references.bib
@@ -2218,3 +2218,17 @@ @article{Engelman1982
   doi = {10.1002/fld.1650020302},
   url = {http://doi.org/10.1002/fld.1650020302},
 }
+
+@article{Shephard1984,
+        doi = {10.1002/nme.1620201112},
+        url = {https://doi.org/10.1002%2Fnme.1620201112},
+        year = 1984,
+        month = {nov},
+        publisher = {Wiley},
+        volume = {20},
+        number = {11},
+        pages = {2107--2112},
+        author = {Mark S. Shephard},
+        title = {Linear multipoint constraints applied via transformation as part of a direct stiffness assembly process},
+        journal = {International Journal for Numerical Methods in Engineering}
+}
diff --git a/include/deal.II/lac/affine_constraints.h b/include/deal.II/lac/affine_constraints.h
@@ -500,12 +500,11 @@ namespace internal
  *
  * @note Many of the algorithms this class implements are discussed in the
  * @ref hp_paper.
- * The algorithms are also related to those shown in <i>M. S. Shephard: Linear
- * multipoint constraints applied via transformation as part of a direct
- * stiffness assembly process. Int. J. Numer. Meth. Engrg., vol. 20 (1984),
- * pp. 2107-2112.</i>, with the difference that the algorithms shown there
- * completely eliminated constrained degrees of freedom, whereas we usually
- * keep them as part of the linear system.
+ * The algorithms are also related to those shown in @cite Shephard1984 ,
+ * with the difference that the algorithms shown there
+ * completely eliminate constrained degrees of freedom, whereas we usually
+ * keep them as part of the linear system (but zero out the row and column
+ * to decouple this degree of freedom from the rest of the linear system).
  *
  * @ingroup dofs
  * @ingroup constraints