From 93f34f514eeb29a761e548071eaf8e3f2bc1c230 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 9 May 2019 10:18:47 -0600
Subject: [PATCH] Clean up various loops in grid_tools.cc.

These loops were quite contorted because of workarounds we needed for MS VC.
Using 'auto' should make this substantially more obvious to read, and while
there one can also use range-based for loops.
---
 source/grid/grid_tools.cc | 62 +++++++--------------------------------
 1 file changed, 10 insertions(+), 52 deletions(-)

diff --git a/source/grid/grid_tools.cc b/source/grid/grid_tools.cc
index 6a181319e3..408e97ab47 100644
--- a/source/grid/grid_tools.cc
+++ b/source/grid/grid_tools.cc
@@ -1479,11 +1479,6 @@ namespace GridTools
                ActiveCellIterator<dim, spacedim, MeshType<dim, spacedim>>::type>
       adjacent_cells;
 
-    typename dealii::internal::
-      ActiveCellIterator<dim, spacedim, MeshType<dim, spacedim>>::type
-        cell = mesh.begin_active(),
-        endc = mesh.end();
-
     // go through all active cells and look if the vertex is part of that cell
     //
     // in 1d, this is all we need to care about. in 2d/3d we also need to worry
@@ -1517,7 +1512,7 @@ namespace GridTools
     // finer and so in the 2d case below we simply add *any* *active* neighbor.
     // in the worst case, we add cells multiple times to the adjacent_cells
     // list, but std::set throws out those cells already entered
-    for (; cell != endc; ++cell)
+    for (const auto &cell : mesh.active_cell_iterators())
       {
         for (unsigned int v = 0; v < GeometryInfo<dim>::vertices_per_cell; v++)
           if (cell->vertex_index(v) == vertex)
@@ -2522,11 +2517,7 @@ namespace GridTools
     // works, but this map can get quite big. Not sure about more efficient
     // solutions.
     std::map<std::pair<unsigned int, unsigned int>, unsigned int> indexmap;
-    for (typename dealii::internal::
-           ActiveCellIterator<dim, spacedim, Triangulation<dim, spacedim>>::type
-             cell = triangulation.begin_active();
-         cell != triangulation.end();
-         ++cell)
+    for (const auto &cell : triangulation.active_cell_iterators())
       indexmap[std::pair<unsigned int, unsigned int>(cell->level(),
                                                      cell->index())] =
         cell->active_cell_index();
@@ -2538,11 +2529,7 @@ namespace GridTools
     // if we only do something if the neighbor has no children -- in that case
     // it is either on the same or a coarser level than we are. in return, we
     // have to add entries in both directions for both cells
-    for (typename dealii::internal::
-           ActiveCellIterator<dim, spacedim, Triangulation<dim, spacedim>>::type
-             cell = triangulation.begin_active();
-         cell != triangulation.end();
-         ++cell)
+    for (const auto &cell : triangulation.active_cell_iterators())
       {
         const unsigned int index = cell->active_cell_index();
         cell_connectivity.add(index, index);
@@ -2550,7 +2537,7 @@ namespace GridTools
           if ((cell->at_boundary(f) == false) &&
               (cell->neighbor(f)->has_children() == false))
             {
-              unsigned int other_index =
+              const unsigned int other_index =
                 indexmap
                   .find(std::pair<unsigned int, unsigned int>(
                     cell->neighbor(f)->level(), cell->neighbor(f)->index()))
@@ -2683,13 +2670,7 @@ namespace GridTools
     // check for an easy return
     if (n_partitions == 1)
       {
-        for (typename dealii::internal::ActiveCellIterator<
-               dim,
-               spacedim,
-               Triangulation<dim, spacedim>>::type cell =
-               triangulation.begin_active();
-             cell != triangulation.end();
-             ++cell)
+        for (const auto &cell : triangulation.active_cell_iterators())
           cell->set_subdomain_id(0);
         return;
       }
@@ -2770,13 +2751,7 @@ namespace GridTools
     // check for an easy return
     if (n_partitions == 1)
       {
-        for (typename dealii::internal::ActiveCellIterator<
-               dim,
-               spacedim,
-               Triangulation<dim, spacedim>>::type cell =
-               triangulation.begin_active();
-             cell != triangulation.end();
-             ++cell)
+        for (const auto &cell : triangulation.active_cell_iterators())
           cell->set_subdomain_id(0);
         return;
       }
@@ -2792,13 +2767,8 @@ namespace GridTools
                              partition_indices,
                              partitioner);
 
-    // finally loop over all cells and set the
-    // subdomain ids
-    for (typename dealii::internal::
-           ActiveCellIterator<dim, spacedim, Triangulation<dim, spacedim>>::type
-             cell = triangulation.begin_active();
-         cell != triangulation.end();
-         ++cell)
+    // finally loop over all cells and set the subdomain ids
+    for (const auto &cell : triangulation.active_cell_iterators())
       cell->set_subdomain_id(partition_indices[cell->active_cell_index()]);
   }
 
@@ -2852,13 +2822,7 @@ namespace GridTools
     // check for an easy return
     if (n_partitions == 1)
       {
-        for (typename dealii::internal::ActiveCellIterator<
-               dim,
-               spacedim,
-               Triangulation<dim, spacedim>>::type cell =
-               triangulation.begin_active();
-             cell != triangulation.end();
-             ++cell)
+        for (const auto &cell : triangulation.active_cell_iterators())
           cell->set_subdomain_id(0);
         return;
       }
@@ -3021,13 +2985,7 @@ namespace GridTools
     if (const parallel::distributed::Triangulation<dim, spacedim> *tr =
           dynamic_cast<const parallel::distributed::Triangulation<dim, spacedim>
                          *>(&triangulation))
-      for (typename dealii::internal::ActiveCellIterator<
-             dim,
-             spacedim,
-             Triangulation<dim, spacedim>>::type cell =
-             triangulation.begin_active();
-           cell != triangulation.end();
-           ++cell)
+      for (const auto &cell : triangulation.active_cell_iterators())
         if (cell->is_artificial() ||
             (cell->is_ghost() &&
              (cell->subdomain_id() < tr->locally_owned_subdomain())))
-- 
2.39.5