Merge branch 'feature/master_grid' into 'master'

Feature/master grid

See merge request !4

dune/multimesh/mmgridfactory.hh

@@ -51,9 +51,8 @@ namespace Dune
     template <class... Args>
     explicit GridFactory (std::size_t n, Args&&... args)
     {
-      gridFactories_.reserve(n);
       for (std::size_t i = 0; i < n; ++i)
-        gridFactories_.emplace_back(std::forward<Args>(args)...);
+        gridFactories_.emplace_back(new GridFactory<HostGrid>{args...});
     }
 
     // initialize at least 1 grid
@@ -68,7 +67,7 @@ namespace Dune
     virtual void insertVertex (const GlobalCoordinate& pos) override
     {
       for (auto& gridFactory : gridFactories_)
-        gridFactory.insertVertex(pos);
+        gridFactory->insertVertex(pos);
     }
 
     /// \brief Insert an element into the coarse grid
@@ -80,7 +79,7 @@ namespace Dune
                                 const std::vector<unsigned int>& vertices) override
     {
       for (auto& gridFactory : gridFactories_)
-        gridFactory.insertElement(type, vertices);
+        gridFactory->insertElement(type, vertices);
     }
 
 
@@ -104,7 +103,7 @@ namespace Dune
       Hybrid::ifElse(Std::is_detected<HasInsertElement, GridFactory<HostGrid>>{},
       [&](auto id) {
         for (auto& gridFactory : gridFactories_)
-          id(gridFactory).insertElement(type, vertices, param);
+          id(gridFactory)->insertElement(type, vertices, param);
       });
     }
 
@@ -117,7 +116,7 @@ namespace Dune
         const std::vector<unsigned int>& vertices) override
     {
       for (auto& gridFactory : gridFactories_)
-        gridFactory.insertBoundarySegment(vertices);
+        gridFactory->insertBoundarySegment(vertices);
     }
 
 
@@ -138,7 +137,7 @@ namespace Dune
       Hybrid::ifElse(Std::is_detected<HasInsertBoundarySegment, GridFactory<HostGrid>>{},
       [&](auto id) {
         for (auto& gridFactory : gridFactories_)
-          id(gridFactory).insertBoundarySegment(vertices, boundarySegment);
+          id(gridFactory)->insertBoundarySegment(vertices, boundarySegment);
       });
     }
 
@@ -152,12 +151,12 @@ namespace Dune
     {
       Grid* multimesh = new Grid{};
       for (auto& gridFactory : gridFactories_)
-        multimesh->grids_.emplace_back(gridFactory.createGrid());
+        multimesh->grids_.emplace_back(gridFactory->createGrid());
       return multimesh;
     }
 
   private:
-    std::vector<GridFactory<HostGrid> > gridFactories_;
+    std::vector<std::unique_ptr<GridFactory<HostGrid>>> gridFactories_;
   };
 
 } // end namespace Dune

dune/multimesh/mmgridview.hh

@@ -223,13 +223,13 @@ namespace Dune
   class MultiMeshLeafGridView
   {
   public:
-    using Traits = MultiMeshLevelGridViewTraits<GridImp>;
+    using Traits = MultiMeshLeafGridViewTraits<GridImp>;
 
     /// The MultiMesh GridType
     using Grid = typename Traits::Grid;
 
     /// Type of the corresponding GridType hosted by the MultiMesh
-    using HostGrid = typename GridImp::HostGridType;
+    using HostGrid = typename GridImp::HostGrid;
 
     using IndexSet = typename Traits::IndexSet;
     using Intersection = typename Traits::Intersection;
@@ -255,7 +255,7 @@ namespace Dune
 
     const HostGrid& grid (std::size_t i) const
     {
-      return multiMesh_->grid(i);
+      return multiMesh_[i];
     }
 
     /// Obtain the level-indexSet

dune/multimesh/mmhierarchiciterator.hh

@@ -22,8 +22,8 @@ namespace Dune
             typename HostGrid::template Codim<0>::Entity>
   {
   private:
-    template <int codim, PartitionIteratorType pitype, class HostGrid_>
-    friend class MultiMeshIterator;
+    template <PartitionIteratorType pitype, class HG, class D>
+    friend class MultiMeshIteratorBase;
 
     using HostEntity = typename HostGrid::template Codim<0>::Entity;
     using EntityTest = std::function<bool(HostEntity)>;

dune/multimesh/mmiterator.hh

@@ -4,295 +4,245 @@
 #define DUNE_MULTIMESH_ITERATOR_HH
 
 #include <numeric>
-#include <stack>
-#include <variant>
+#include <vector>
 
 #include <dune/common/iteratorfacades.hh>
-#include <dune/common/std/type_traits.hh>
-#include <dune/grid/common/exceptions.hh>
 #include <dune/grid/common/gridenums.hh>
 
 #include "mmentity.hh"
 #include "mmhierarchiciterator.hh"
+#include "mmiteratorbase.hh"
 
 namespace Dune
 {
-  /** \brief Iterator over all entities of a given codimension and level of a grid.
-   *  \ingroup MultiMesh
-   */
   template <int codim, PartitionIteratorType pitype, class HostGrid>
-  class MultiMeshIterator
+  class MultiMeshLevelIterator : public DummyIterator
   {
-  public:
-    template <class... Args>
-    MultiMeshIterator(Args&&... args)
-    {
-      DUNE_THROW(NotImplemented, "Not implemented for entity of codim != 0!");
-    }
-
-    int operator*() const { return 0; }
-    MultiMeshIterator& operator++() { return *this; }
-    MultiMeshIterator operator++(int) { return *this; }
-    bool operator!=(MultiMeshIterator const&) const { return false; }
+    using DummyIterator::DummyIterator;
   };
 
-
-  // Implemented for codim 0 entities only
   template <PartitionIteratorType pitype, class HostGrid>
-  class MultiMeshIterator<0, pitype, HostGrid>
-      : public ForwardIteratorFacade<MultiMeshIterator<0,pitype,HostGrid>,
-            MultiEntity<HostGrid>,
-            MultiEntity<HostGrid> const&>
+  class MultiMeshLevelIterator<0,pitype,HostGrid>
+      : public MultiMeshIteratorBase<pitype,HostGrid,MultiMeshLevelIterator<0,pitype,HostGrid>>
   {
-  private:
-    // LevelIterator to the equivalent entity in the host grid
-    using HostGridLevelIterator =
-      typename HostGrid::template Codim<0>::template Partition<pitype>::LevelIterator;
-
+    using Self = MultiMeshLevelIterator;
+    using Super = MultiMeshIteratorBase<pitype,HostGrid,Self>;
     using HostEntity = typename HostGrid::template Codim<0>::Entity;
-
-    using EntityTest  = typename MultiMeshHierarchicIterator<HostGrid>::EntityTest;
-    using EntityStack = typename MultiMeshHierarchicIterator<HostGrid>::EntityStack;
+    using EntityTest = typename Super::EntityTest;
 
   public:
-    /// Constructor. Stores a pointer to the grid
+    // Level iterator
     template <class GridImp>
-    MultiMeshIterator (const GridImp* multiMesh, int level)
-      : incrementAllowed_(multiMesh->size(), true)
+    MultiMeshLevelIterator (tag::begin_iterator, const GridImp* multiMesh, int level)
+      : Super{tag::begin_iterator{}, multiMesh}
+      , incrementAllowed_(multiMesh->size(), true)
       , contains_(multiMesh->size(), EntityTest{[level](const HostEntity& entity) { return entity.level() == level; }})
-      , maxLevel_(multiMesh->size(), level)
       , multiEntity_(multiMesh->size())
     {
-      for (auto const& grid : multiMesh->grids_) {
-        macroIterators_.push_back(grid->levelGridView(0).template begin<0,pitype>());
-        macroEndIterators_.push_back(grid->levelGridView(0).template end<0,pitype>());
-      }
-
-      // go to first leaf entity on all grids
-      entityStacks_.reserve(multiMesh->size());
-      for (std::size_t i = 0; i < multiMesh->size(); ++i) {
-        maxLevel_[i] = (*multiMesh)[i].maxLevel();
-        entityStacks_.emplace_back((*multiMesh)[i].maxLevel());
-        initialIncrement(i);
-      }
+      this->initialIncrement();
     }
 
-    /// Constructor which create the end iterator
-    /**
-     * \param  multiMesh  Pointer to grid instance
-     * \param  endDummy   Here only to distinguish it from the other constructor
-     */
+    // End iterator
     template <class GridImp>
-    MultiMeshIterator (const GridImp* multiMesh, int level, bool endDummy)
+    MultiMeshLevelIterator (tag::end_iterator, const GridImp* multiMesh, int level = -1)
+      : Super{tag::end_iterator{}, multiMesh}
+    {}
+
+    void initialIncrement_impl ()
     {
-      for (auto const& grid : multiMesh->grids_)
-        macroIterators_.push_back(grid->levelGridView(0).template end<0,pitype>());
+      for (std::size_t i = 0; i < this->size(); ++i)
+        this->initialIncrement(i);
     }
 
-    /// Constructor which create the leaf-iterator
-    template <class GridImp>
-    MultiMeshIterator (const GridImp* multiMesh)
-      : MultiMeshIterator{multiMesh, -1}
-    {}
+    void increment_impl ()
+    {
+      for (std::size_t i = 0; i < this->size(); ++i)
+        incrementAllowed_[i] = this->incrementAllowed(i);
 
-    /// Constructor which create the end leaf-iterator
-    template <class GridImp>
-    MultiMeshIterator (const GridImp* multiMesh, bool endDummy)
-      : MultiMeshIterator{multiMesh, -1, endDummy}
-    {}
+      for (std::size_t i = 0; i < this->size(); ++i) {
+        if (incrementAllowed_[i])
+          this->increment(i);
+      }
+    }
 
-    /// Construct an iterator from n gridViews of possibly different type
-    template <class... GridViews,
-      std::enable_if_t<not Std::disjunction<std::is_same<GridViews,bool>...>::value, int> = 0>
-    MultiMeshIterator (GridViews const&... gridViews)
-      : incrementAllowed_(sizeof...(GridViews), true)
-      , maxLevel_{gridViews.grid().maxLevel()...}
-      , multiEntity_(sizeof...(GridViews))
-      , macroIterators_{gridViews.grid().levelGridView(0).template begin<0,pitype>()...}
-      , macroEndIterators_{gridViews.grid().levelGridView(0).template end<0,pitype>()...}
-      , entityStacks_{EntityStack{gridViews.grid().maxLevel()}...}
+    const MultiEntity<HostGrid>& dereference_impl () const
     {
-      contains_.reserve(sizeof...(GridViews));
-      Hybrid::forEach(std::forward_as_tuple(gridViews...), [this](auto const& gv) {
-        contains_.emplace_back([gv](const HostEntity& entity) { return gv.contains(entity); });
-      });
+      // update entries in multiEntity that have changed
+      for (std::size_t i = 0; i <  this->size(); ++i) {
+        if (incrementAllowed_[i])
+          multiEntity_[i] = this->dereference(i);
+      }
+      return multiEntity_;
+    }
 
-      for (std::size_t i = 0; i < sizeof...(GridViews); ++i)
-        initialIncrement(i);
+    bool levelReached_impl (std::size_t i, const HostEntity& entity) const
+    {
+      return contains_[i](entity) || entity.isLeaf();
     }
 
-    template <class... GridViews>
-    MultiMeshIterator (bool endDummy, GridViews const&... gridViews)
-      : macroIterators_{gridViews.grid().levelGridView(0).template end<0,pitype>()...}
-    {}
+  private:
+    std::vector<bool> incrementAllowed_;
+    std::vector<EntityTest> contains_;
+    mutable MultiEntity<HostGrid> multiEntity_;
+  };
 
-#if DUNE_HAVE_CXX_VARIANT
-    /// Construct an iterator from a vector of GridViews, where each GridView can be
-    /// either a leaf- or a level-gridView, thus we need to use a variant.
-    template <class... GV>
-    MultiMeshIterator (const std::vector<std::variant<GV...>>& gridViews)
-      : incrementAllowed_(gridViews.size(), true)
-      , multiEntity_(gridViews.size())
-    {
-      contains_.reserve(gridViews.size());
-      entityStacks_.reserve(gridViews.size());
-      maxLevel_.reserve(gridViews.size());
-
-      for (auto const& gvs : gridViews) {
-        macroIterators_.push_back(std::visit([](auto const& gv) {
-          return gv.grid().levelGridView(0).template begin<0,pitype>(); }, gvs));
-        macroEndIterators_.push_back(std::visit([](auto const& gv) {
-          return gv.grid().levelGridView(0).template end<0,pitype>(); }, gvs));
-        contains_.emplace_back(std::visit([](auto const& gv) {
-          return EntityTest{[gv](const HostEntity& entity) { return gv.contains(entity); }}; }, gvs));
-        maxLevel_.push_back(std::visit([](auto const& gv) { return gv.grid().maxLevel(); }, gvs));
-        entityStacks_.emplace_back(std::visit([](auto const& gv) { return gv.grid().maxLevel(); }, gvs));
-      }
 
-      // go to first leaf entity on all grids
-      for (std::size_t i = 0; i < entityStacks_.size(); ++i)
-        initialIncrement(i);
+  template <int codim, PartitionIteratorType pitype, class HostGrid>
+  class MultiMeshLeafIterator : public DummyIterator
+  {
+    using DummyIterator::DummyIterator;
+  };
+
+  template <PartitionIteratorType pitype, class HostGrid>
+  class MultiMeshLeafIterator<0,pitype,HostGrid>
+      : public MultiMeshIteratorBase<pitype,HostGrid,MultiMeshLeafIterator<0,pitype,HostGrid>>
+  {
+    using Self = MultiMeshLeafIterator;
+    using Super = MultiMeshIteratorBase<pitype,HostGrid,Self>;
+    using HostEntity = typename HostGrid::template Codim<0>::Entity;
+
+  public:
+    // Leaf iterator
+    template <class GridImp>
+    MultiMeshLeafIterator (tag::begin_iterator, const GridImp* multiMesh)
+      : Super{tag::begin_iterator{}, multiMesh}
+      , incrementAllowed_(multiMesh->size(), true)
+      , multiEntity_(multiMesh->size())
+    {
+      this->initialIncrement();
     }
 
-    template <class... GV>
-    MultiMeshIterator (const std::vector<std::variant<GV...>>& gridViews, bool endDummy)
+    // End iterator
+    template <class GridImp>
+    MultiMeshLeafIterator (tag::end_iterator, const GridImp* multiMesh)
+      : Super{tag::end_iterator{}, multiMesh}
+    {}
+
+    void initialIncrement_impl ()
     {
-      for (auto const& gvs : gridViews) {
-        macroIterators_.push_back(std::visit([](auto const& gv) {
-          return gv.grid().levelGridView(0).template end<0,pitype>(); }, gvs));
-      }
+      for (std::size_t i = 0; i < this->size(); ++i)
+        this->initialIncrement(i);
     }
-#endif
 
-    /// prefix increment
-    void increment ()
+    void increment_impl ()
     {
-      for (std::size_t i = 0; i < entityStacks_.size(); ++i)
-        incrementAllowed_[i] = incrementAllowed(i);
+      for (std::size_t i = 0; i < this->size(); ++i)
+        incrementAllowed_[i] = this->incrementAllowed(i);
 
-      for (std::size_t i = 0; i < entityStacks_.size(); ++i) {
+      for (std::size_t i = 0; i < this->size(); ++i) {
         if (incrementAllowed_[i])
-          increment(i);
+          this->increment(i);
       }
     }
 
-    /// dereferencing
-    MultiEntity<HostGrid> const& dereference () const
+    const MultiEntity<HostGrid>& dereference_impl () const
     {
       // update entries in multiEntity that have changed
-      for (std::size_t i = 0; i < entityStacks_.size(); ++i) {
+      for (std::size_t i = 0; i <  this->size(); ++i) {
         if (incrementAllowed_[i])
-          multiEntity_[i] = dereference(i);
+          multiEntity_[i] = this->dereference(i);
       }
       return multiEntity_;
     }
 
-    /// equality
-    bool equals (const MultiMeshIterator& that) const
+    bool levelReached_impl (std::size_t /*i*/, const HostEntity& entity) const
     {
-      return macroIterators_ == that.macroIterators_;
+      return entity.isLeaf();
     }
 
-  protected:
-    // got to next entity in grid i
-    void increment (std::size_t i)
-    {
-      auto& entityStack = entityStacks_[i];
-      auto& macroIt = macroIterators_[i];
-      auto const& macroEnd = macroEndIterators_[i];
-
-      // 1. go up in tree or to next entity on current level until we can go down again
-      while (!entityStack.empty()) {
-        auto& top = entityStack.top();
-        ++top.it;
-        if (top.it == top.end) {
-          entityStack.pop();
-        } else {
-          break;
-        }
-      }
+  private:
+    std::vector<bool> incrementAllowed_;
+    mutable MultiEntity<HostGrid> multiEntity_;
+  };
 
-      // 2. if entityStack is empty, go to next macroElement
-      if (entityStack.empty()) {
-        ++macroIt;
-        if (macroIt == macroEnd)
-          return;
-      }
 
-      // 3. go down in tree until leaf entity
-      auto child = dereference(i);
-      for (; !(contains_[i](child) || child.isLeaf()); child = dereference(i)) {
-        assert(child.isRegular() && "No irregular elements allowed in multi-mesh traversal");
-        entityStack.emplace(child);
-        assert(entityStack.size() <= maxLevel_[i]);
-      }
+  template <int codim, PartitionIteratorType pitype, class HostGrid>
+  class MultiMeshMasterLeafIterator : public DummyIterator
+  {
+    using DummyIterator::DummyIterator;
+  };
+
+  template <PartitionIteratorType pitype, class HostGrid>
+  class MultiMeshMasterLeafIterator<0,pitype,HostGrid>
+      : public MultiMeshIteratorBase<pitype,HostGrid,MultiMeshMasterLeafIterator<0,pitype,HostGrid>>
+  {
+    using Self = MultiMeshMasterLeafIterator;
+    using Super = MultiMeshIteratorBase<pitype,HostGrid,Self>;
+    using HostEntity = typename HostGrid::template Codim<0>::Entity;
 
-      // assert(contains_[i](child) && "No valid child element found in gridView");
+  public:
+    // Leaf iterator
+    template <class GridImp>
+    MultiMeshMasterLeafIterator (tag::begin_iterator, const GridImp* multiMesh, std::size_t master)
+      : Super{tag::begin_iterator{}, multiMesh}
+      , incrementAllowed_(multiMesh->size(), true)
+      , level_(multiMesh->size())
+      , multiEntity_(multiMesh->size())
+      , master_(master)
+    {
+      this->initialIncrement();
     }
 
-    /// Return true, if all stacks with size > stack[i].size are finished
-    bool incrementAllowed (std::size_t i) const
+    // End iterator
+    template <class GridImp>
+    MultiMeshMasterLeafIterator (tag::end_iterator, const GridImp* multiMesh)
+      : Super{tag::end_iterator{}, multiMesh}
+    {}
+
+    // first increment the master grid then the others
+    void initialIncrement_impl ()
     {
-      std::size_t size = entityStacks_[i].size();
-      return std::accumulate(entityStacks_.begin(), entityStacks_.end(), true,
-        [i,size](bool allowed, auto const& entityStack) {
-          return allowed && (entityStack.size() <= size || entityStack.finished(size));
-        });
+      level_[master_] = this->initialIncrement(master_);
+      for (std::size_t i = 0; i < this->size(); ++i)
+        if (i != master_)
+          level_[i] = this->initialIncrement(i);
     }
 
-    // got to first leaf entity on grid i
-    void initialIncrement (std::size_t i)
+    // first increment the master grid then the others
+    void increment_impl ()
     {
-      auto& entityStack = entityStacks_[i];
-      auto& macroIt = macroIterators_[i];
-      auto const& macroEnd = macroEndIterators_[i];
-
-      assert(entityStack.empty());
-      if (macroIt == macroEnd)
-        return;
-
-      // 1. go down in tree until leaf entity
-      auto child = dereference(i);
-      for (; !(contains_[i](child) || child.isLeaf()); child = dereference(i)) {
-        assert(child.isRegular() && "No irregular elements allowed in multi-mesh traversal");
-        entityStack.emplace(child);
-        assert(entityStack.size() <= maxLevel_[i]);
+      for (std::size_t i = 0; i < this->size(); ++i)
+        incrementAllowed_[i] = this->incrementAllowed(i);
+
+      if (incrementAllowed_[master_])
+        level_[master_] = this->increment(master_);
+      for (std::size_t i = 0; i < this->size(); ++i) {
+        if (i != master_ && incrementAllowed_[i])
+          level_[i] = this->increment(i);
       }
-
-      // assert(contains_[i](child) && "No valid child element found in gridView");
     }
 
-    HostEntity dereference (std::size_t i) const
+    const MultiEntity<HostGrid>& dereference_impl () const
     {
-      if (entityStacks_[i].empty()) {
-        assert(macroIterators_[i] != macroEndIterators_[i]);
-        return *macroIterators_[i];
-      } else {
-        assert(entityStacks_[i].top().it != entityStacks_[i].top().end);
-        return *entityStacks_[i].top().it;
+      // update entries in multiEntity that have changed
+      for (std::size_t i = 0; i <  this->size(); ++i) {
+        if (incrementAllowed_[i])
+          multiEntity_[i] = this->dereference(i);
       }
+      return multiEntity_;
+    }
+
+    // got down to leaf entity on master grid and until the master grid level for the other grids
+    bool levelReached_impl (std::size_t i, const HostEntity& entity) const
+    {
+      return (i == master_ && entity.isLeaf()) || entity.level() == level_[master_];
     }
 
   private:
     std::vector<bool> incrementAllowed_;
-    std::vector<EntityTest> contains_;
-    std::vector<int> maxLevel_;
-
+    std::vector<int> level_;
     mutable MultiEntity<HostGrid> multiEntity_;
-
-    std::vector<HostGridLevelIterator> macroIterators_;
-    std::vector<HostGridLevelIterator> macroEndIterators_;
-    std::vector<EntityStack> entityStacks_;
+    std::size_t master_;
   };
 
-  template <class... GridViews>
-  inline auto multi_elements(GridViews const&... gridViews)
+
+  template <PartitionIteratorType pitype = All_Partition, class Grid>
+  inline auto master_leaf_elements(Grid const& multiMesh, std::size_t master)
   {
-    using GridView0 = std::tuple_element_t<0,std::tuple<GridViews...>>;
-    using Iterator = MultiMeshIterator<0,All_Partition,typename GridView0::Grid>;
+    using Iterator = MultiMeshMasterLeafIterator<0,pitype,typename Grid::HostGrid>;
     using Range = IteratorRange<Iterator>;
-    return Range{ Iterator{gridViews...},
-                  Iterator{true, gridViews...} };
+    return Range{ Iterator{tag::begin_iterator{}, &multiMesh, master},
+                  Iterator{tag::end_iterator{}, &multiMesh} };
   }
 
 }  // end namespace Dune

dune/multimesh/mmiteratorbase.hh

+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+#ifndef DUNE_MULTIMESH_ITERATOR_BASE_HH
+#define DUNE_MULTIMESH_ITERATOR_BASE_HH
+
+#include <numeric>
+#include <stack>
+#include <type_traits>
+
+#include <dune/common/std/type_traits.hh>
+#include <dune/grid/common/gridenums.hh>
+
+#include "mmentity.hh"
+#include "mmhierarchiciterator.hh"
+#include "mmiteratorinterface.hh"
+
+namespace Dune
+{
+  template <PartitionIteratorType pitype, class HostGrid, class Derived>
+  class MultiMeshIteratorBase
+      : public MultiMeshIteratorInterface<HostGrid,Derived>
+  {
+    using Super = MultiMeshIteratorInterface<HostGrid,Derived>;
+
+  protected:
+    // LevelIterator to the equivalent entity in the host grid
+    using HostGridLevelIterator =
+      typename HostGrid::template Codim<0>::template Partition<pitype>::LevelIterator;
+
+    template <class GV>
+    using IsGridView = Std::disjunction<
+      std::is_same<std::decay_t<GV>,typename HostGrid::LeafGridView>,
+      std::is_same<std::decay_t<GV>,typename HostGrid::LevelGridView> >;
+
+    using HostEntity = typename HostGrid::template Codim<0>::Entity;
+
+    using EntityTest = typename MultiMeshHierarchicIterator<HostGrid>::EntityTest;
+    using EntityStack = typename MultiMeshHierarchicIterator<HostGrid>::EntityStack;
+
+  public:
+
+    /// Constructor which creates the begin iterator
+    /**
+     * \param  multiMesh  Pointer to grid instance
+     */
+    template <class GridImp>
+    MultiMeshIteratorBase (tag::begin_iterator, const GridImp* multiMesh)
+      : maxLevel_(multiMesh->size())
+    {
+      for (std::size_t i = 0; i < multiMesh->size(); ++i) {
+        macroIterators_.push_back(multiMesh->levelGridView(i,0).template begin<0,pitype>());
+        macroEndIterators_.push_back(multiMesh->levelGridView(i,0).template end<0,pitype>());