smooth_partition_bounds.h

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/*
 * Copyright (c) 2015:  G-CSC, Goethe University Frankfurt
 * Author: Sebastian Reiter
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 */
 
#ifndef __H__UG_smooth_partition_bounds
#define __H__UG_smooth_partition_bounds
 
#include "../partitioner.h"
#include "lib_grid/iterators/lg_for_each.h"
 
namespace ug{
 
template <class elem_t>/*, int dim>*/
class SmoothPartitionBounds : public IPartitionPostProcessor
{
  public:
    SmoothPartitionBounds() :
      m_mg(NULL),
      m_partitions(NULL)
      // m_consideringVerticalSidesOnly(false)
    {}
 
    virtual ~SmoothPartitionBounds()
    {
      if(m_mg && m_mg->has_attachment<side_t>(m_aSubsetNbrs))
        m_mg->detach_from<side_t>(m_aSubsetNbrs);
    }
 
    void init_post_processing(MultiGrid* mg, SubsetHandler* partitions)
    {
      m_mg = mg;
      m_partitions = partitions;
      mg->attach_to<side_t>(m_aSubsetNbrs);
    }
 
    // void set_position_attachment(position_attachment_t aPos);
 
    // void consider_vertical_sides_only(bool enable)
    // {
    //  m_consideringVerticalSidesOnly = enable;
    //  if(enable){
    //    UG_COND_THROW(!mg->has_vertex_attachment(m_aPos),
    //            "consider_vertical_sides_only may only be enabled if "
    //            "a valid position attachment for the underlying grid "
    //            "has been set previously.");
    //    m_aaPos.access(*mg, m_aPos);
    //  }
    // }
    
    // bool considering_vertical_sides_only() const {return m_consideringVerticalSidesOnly;}
 
    void post_process(int partitionLvl)
    {
      using namespace std;
    //  we'll regularize the partition to reduce h-interface sizes
    //  (also important to improve gmg-smoother efficiency).
    //todo: PARALLEL IMPLEMENTATION, EQUALLY DISTRIBUTE SWAP-ELEMENTS
      MultiGrid& mg = *m_mg;
      SubsetHandler& sh = *m_partitions;
 
      Grid::AttachmentAccessor<side_t, a_subset_pair_t> aaSubsetNbrs(mg, m_aSubsetNbrs);
 
      typename MultiGrid::traits<side_t>::secure_container  sides;
      
      vector<int> nbrSubs;
      bool assignToSmallerSubsetsOnly = true;
 
      for(int main_iteration = 0; main_iteration < 2; ++main_iteration){
        SetAttachmentValues(aaSubsetNbrs, mg.begin<side_t>(partitionLvl),
                  mg.end<side_t>(partitionLvl), pair<int, int>(-1, -1));
 
      //  regularization step 1: assign element-subset-indices to sides
        lg_for_each_in_lvl_template(elem_t, e, mg, partitionLvl){
          int si = sh.get_subset_index(e);
          if(si >= 0){
            mg.associated_elements(sides, e);
            for_each_in_vec(side_t* s, sides){
              if(aaSubsetNbrs[s].first == -1)
                aaSubsetNbrs[s].first = si;
              else
                aaSubsetNbrs[s].second = si;
            }end_for;
          }
        }end_for;
 
      //todo: regularization step 1.5: communicate subsetNbrs
      //  ...
      
      //  regularization step 2: check for elements whose neighbors belong to other partitions
        lg_for_each_in_lvl_template(elem_t, e, mg, partitionLvl){
          int si = sh.get_subset_index(e);
          if(si >= 0){
            nbrSubs.clear();
            mg.associated_elements(sides, e);
            int numOwnSubsetNbrs = 0;
            for_each_in_vec(side_t* s, sides){
              if(s->reference_object_id() == ROID_QUADRILATERAL){
                const subset_pair_t& nbrs = aaSubsetNbrs[s];
                if(nbrs.first == si && nbrs.second == si)
                  ++numOwnSubsetNbrs;
                else if(nbrs.first != -1 && nbrs.first != si)
                  nbrSubs.push_back(nbrs.first);
                else if(nbrs.second != -1 && nbrs.second != si)
                  nbrSubs.push_back(nbrs.second);
              }
            }end_for;
 
          //  we'll now search for the subset which shares the most sides.
            int newSubsetNbrs = numOwnSubsetNbrs;
            int newSub = si;
 
            for(size_t i_nbrSub = 0; i_nbrSub < nbrSubs.size(); ++i_nbrSub){
              int nbrSub = nbrSubs[i_nbrSub];
              if(nbrSub != -1){// otherwise the subset has already been processed
                int count = 1;
                for(size_t i = i_nbrSub + 1; i < nbrSubs.size(); ++i){
                  if(nbrSubs[i] == nbrSub){
                    nbrSubs[i] = -1;
                    ++count;
                  }
                }
 
                if(count > newSubsetNbrs){
                  newSubsetNbrs = count;
                  newSub = nbrSub;
                }
              }
            }
 
          //  assign the new subset.
          //todo: use a more elaborate decider to which subset an element shall be assigned.
            if(newSub != -1
               && ((assignToSmallerSubsetsOnly && newSub < si)
                   || (!assignToSmallerSubsetsOnly && newSub != si)))
            {
              sh.assign_subset(e, newSub);
            }
          }
        }end_for;
 
      //  in the second iteration we'll assign to all neighbors
        assignToSmallerSubsetsOnly = false;
      }
    }
 
    void partitioning_done()
    {
      m_mg->detach_from<side_t>(m_aSubsetNbrs);
    }
 
  private:
    typedef typename elem_t::side   side_t;
    typedef std::pair<int, int>     subset_pair_t;
    typedef Attachment<subset_pair_t> a_subset_pair_t;
    
    MultiGrid*    m_mg;
    SubsetHandler*  m_partitions;
    a_subset_pair_t m_aSubsetNbrs;
    // bool     m_consideringVerticalSidesOnly;
};
 
}// end of namespace
 
#endif  //__H__UG_smooth_partition_bounds