Merge pull request #3431 from lindsayad/reduce-setup-time-for-fv

Exploring how to reduce setup time for large-element-stencil simulations

Author: lindsayad

include/base/dof_object.h

@@ -1380,6 +1380,23 @@ struct CompareDofObjectsByID
   }
 };
 
+struct CompareDofObjectsByPIDAndThenID
+{
+  bool operator()(const DofObject * a,
+                  const DofObject * b) const
+  {
+    libmesh_assert (a);
+    libmesh_assert (b);
+
+    if (a->processor_id() < b->processor_id())
+      return true;
+    if (b->processor_id() < a->processor_id())
+      return false;
+
+    return a->id() < b->id();
+  }
+};
+
 } // namespace libMesh
 
 

include/base/ghosting_functor.h

@@ -25,6 +25,7 @@
 #include "libmesh/id_types.h"
 #include "libmesh/mesh_base.h"
 #include "libmesh/reference_counted_object.h"
+#include "libmesh/dof_object.h"
 
 // C++ Includes
 #include <unordered_map>
@@ -228,7 +229,7 @@ class GhostingFunctor : public ReferenceCountedObject<GhostingFunctor>
    * What elements do we care about and what variables do we care
    * about on each element?
    */
-  typedef std::unordered_map<const Elem*, const CouplingMatrix*> map_type;
+  typedef std::map<const Elem*, const CouplingMatrix*, CompareDofObjectsByPIDAndThenID> map_type;
 
   /**
    * For the specified range of active elements, what other elements

include/base/sparsity_pattern.h

@@ -249,38 +249,15 @@ void SparsityPattern::sort_row (const BidirectionalIterator begin,
                                 BidirectionalIterator       middle,
                                 const BidirectionalIterator end)
 {
-  if ((begin == middle) || (middle == end)) return;
-
-  libmesh_assert_greater (std::distance (begin,  middle), 0);
-  libmesh_assert_greater (std::distance (middle, end), 0);
-  libmesh_assert (std::unique (begin,  middle) == middle);
-  libmesh_assert (std::unique (middle, end) == end);
-
-  while (middle != end)
-    {
-      BidirectionalIterator
-        b = middle,
-        a = b-1;
-
-      // Bubble-sort the middle value downward
-      while (!(*a < *b)) // *a & *b are less-than comparable, so use <
-        {
-          std::swap (*a, *b);
-
-#if defined(__GNUC__) && (__GNUC__ < 4) && !defined(__INTEL_COMPILER)
-          /* Prohibit optimization at this point since gcc 3.3.5 seems
-             to have a bug.  */
-          SparsityPattern::_dummy_function();
+  // Assure we have the conditions for an inplace_merge
+#ifdef DEBUG
+  libmesh_assert(std::is_sorted(begin, middle));
+  libmesh_assert(std::is_sorted(middle, end));
 #endif
+  libmesh_assert(std::unique(begin, middle) == middle);
+  libmesh_assert(std::unique(middle, end) == end);
 
-          if (a == begin) break;
-
-          b=a;
-          --a;
-        }
-
-      ++middle;
-    }
+  std::inplace_merge(begin, middle, end);
 
   // Assure the algorithm worked if we are in DEBUG mode
 #ifdef DEBUG

tests/base/overlapping_coupling_test.C

@@ -67,7 +67,7 @@ class OverlappingCouplingFunctor : public GhostingFunctor
   (const MeshBase::const_element_iterator & range_begin,
    const MeshBase::const_element_iterator & range_end,
    processor_id_type p,
-   std::unordered_map<const Elem *,const CouplingMatrix*> & coupled_elements) override
+   map_type & coupled_elements) override
   {
     std::unique_ptr<PointLocatorBase> sub_point_locator = _mesh.sub_point_locator();
 
@@ -430,8 +430,8 @@ private:
 
     OverlappingCouplingFunctor coupling_functor(system);
 
-    std::unordered_map<const Elem *,const CouplingMatrix*> subdomain_one_couplings;
-    std::unordered_map<const Elem *,const CouplingMatrix*> subdomain_two_couplings;
+    GhostingFunctor::map_type subdomain_one_couplings;
+    GhostingFunctor::map_type subdomain_two_couplings;
 
     coupling_functor( _mesh->active_subdomain_elements_begin(1),
                       _mesh->active_subdomain_elements_end(1),