From: Wolfgang Bangerth Date: Tue, 14 Aug 2018 19:21:28 +0000 (-0600) Subject: Add a glossary entry for the term 'coarse mesh'. X-Git-Tag: v9.1.0-rc1~813^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ea0b08df5b3d9ba4ea95ae89905868b6d30ea4d5;p=dealii.git Add a glossary entry for the term 'coarse mesh'. --- diff --git a/doc/doxygen/headers/glossary.h b/doc/doxygen/headers/glossary.h index a9fb7e8eec..24c2616624 100644 --- a/doc/doxygen/headers/glossary.h +++ b/doc/doxygen/headers/glossary.h @@ -377,7 +377,42 @@ * parallel::distributed::Triangulation . * * - * @see @ref boundary "The module on boundaries" + * @see @ref boundary "The module on boundaries". + * + * + *
@anchor GlossCoarseMesh Coarse mesh
+ *
+ * A "coarse mesh" in deal.II is a triangulation object that consists only + * of cells that are not refined, i.e., a mesh in which no cell is a child + * of another cell. This is generally how triangulations are first + * constructed in deal.II, for example using (most of) the functions in + * namespace GridGenerator, the functions in class GridIn, or directly + * using the function Triangulation::create_triangulation(). One can of + * course do computations on such meshes, but most of the time (see, for + * example, almost any of the tutorial programs) one first refines the + * coarse mesh globally (using Triangulation::refine_global()), + * or adaptively (in that case first computing a refinement + * criterion, then one of the functions in namespace GridRefinement, + * and finally calling + * Triangulation::execute_coarsening_and_refinement()). The mesh is + * then no longer a "coarse mesh", but a "refined mesh". + * + * In some contexts, we also use the phrase "the coarse mesh of a + * triangulation", and by that mean that set of cells that the triangulation + * started out with, i.e., from which all the currently + * @ref GlossActive "active cells" of the triangulation have been obtained + * by mesh refinement. (Some of the coarse mesh cells may of course also + * be active if they have never been refined.) + * + * Triangulation objects store cells in levels: in + * particular, all cells of a coarse mesh are on level zero. Their + * children (if we executed Triangulation::refine_global(1) on a + * coarse mesh) would then be at level one, etc. The coarse mesh of a + * triangulation (in the sense of the previous paragraph) then + * consists of exactly the level-zero cells of a triangulation. (Whether + * they are active (i.e., have no children) or have been refined is not + * important for this definition.) + *
* * *
@anchor GlossColorization Colorization
@@ -402,6 +437,7 @@ * * * + * *
@anchor GlossComponent Component
* *
When considering systems of equations in which the solution is not @@ -571,7 +607,8 @@ * the operation that these compress() functions invoke applies * to adding elements or setting them. In some cases, not all processors may * be adding elements, for example if a processor does not own any cells when - * using a very coarse (initial) mesh. For this reason, compress() takes an + * using a very @ref GlossCoarseMesh "coarse (initial) mesh". + * For this reason, compress() takes an * argument of type VectorOperation, which can be either ::%add, or ::%insert. * This argument is required for vectors and matrices starting with the 7.3 * release. @@ -757,14 +794,14 @@ * @image html distorted_3d.png "A well-formed, a pinched, and a twisted cell in 3d." * * Distorted cells can appear in two different ways: The original - * coarse mesh can already contain such cells, or they can be created - * as the result of mesh refinement if the boundary description in use - * is sufficiently irregular. + * @ref GlossCoarseMesh "coarse mesh" can already contain such cells, + * or they can be created as the result of mesh refinement if the boundary + * description in use is sufficiently irregular. * * If the appropriate flag is given upon creation of a triangulation, * the function Triangulation::create_triangulation, which is called * by the various functions in GridGenerator and GridIn (but can also - * be called from user code, see step-14, will signal + * be called from user code, see step-14), will signal * the creation of coarse meshes with distorted cells by throwing an * exception of type Triangulation::DistortedCellList. There are * legitimate cases for creating meshes with distorted cells (in @@ -817,10 +854,10 @@ * The problem with that is, of course, that the bottom two child cells are * twisted, whereas the top two children are well-shaped. While such * meshes can happen with sufficiently irregular boundary descriptions - * (and if the coarse mesh is entirely inadequate to resolve the - * complexity of the boundary), the Triangulation class does not know - * what to do in such situations unless one attaches an appropriate manifold - * object to the cells in question (see the + * (and if the @ref GlossCoarseMesh "coarse mesh" is entirely inadequate + * to resolve the complexity of the boundary), the Triangulation class does not + * know what to do in such situations unless one attaches an appropriate + * manifold object to the cells in question (see the * @ref manifold "documentation module on manifolds"). Consequently, absent * such a manifold description or if the manifold description does not * provide a sufficient description of the geometry, the @@ -985,10 +1022,10 @@ * If a mesh is distributed across multiple MPI processes using the * parallel::distributed::Triangulation class, each processor stores * only the cells it owns, one layer of adjacent cells that are owned - * by other processors, all coarse level cells, and all cells that are - * necessary to maintain the invariant that adjacent cells must differ - * by at most one refinement level. The cells stored on each process - * that are not owned by this process but that are adjacent to the + * by other processors, all @ref GlossCoarseMesh "coarse level cells", + * and all cells that are necessary to maintain the invariant that adjacent + * cells must differ by at most one refinement level. The cells stored on + * each process that are not owned by this process but that are adjacent to the * ones owned by this process are called "ghost cells", and for these * cells the predicate cell-@>is_ghost() returns * true. Ghost cells are guaranteed to exist in the globally @@ -1672,7 +1709,8 @@ * subdomain ids are only assigned to cells that the current processor * owns as well as the immediately adjacent @ref GlossGhostCell "ghost cells". * Cells further away are held on each processor to ensure - * that every MPI process has access to the full coarse grid as well + * that every MPI process has access to the full + * @ref GlossCoarseMesh "coarse grid" as well * as to ensure the invariant that neighboring cells differ by at most * one refinement level. These cells are called "artificial" (see * @ref GlossArtificialCell "here") and have the special subdomain id value @@ -1863,8 +1901,9 @@ * * By default, if you write a loop over all cells in deal.II, the cells * will be traversed in an order where coarser cells (i.e., cells that were - * obtained from coarse mesh cells with fewer refinement steps) come before - * cells that are finer (i.e., cells that were obtained with more refinement + * obtained from + * @ref GlossCoarseMesh "coarse mesh" cells with fewer refinement steps) come + * before cells that are finer (i.e., cells that were obtained with more refinement * steps). Within each refinement level, cells are traversed in an order * that has something to do with the order in which they were created; * in essence, however, this order is best of thought of as "unspecified": @@ -1894,7 +1933,7 @@ * To explain the concept of the Z order, consider the following sequence * of meshes (with each cell numbered using the "level.index" notation, * where "level" is the number of refinements necessary to get from a - * coarse mesh cell to a particular cell, and "index" the index of this + * @ref GlossCoarseMesh "coarse mesh" cell to a particular cell, and "index" the index of this * cell within a particular refinement level): * * @image html simple-mesh-0.png "A coarse mesh"