load_balancing_impl.hpp

Go to the documentation of this file.

/*
 * Copyright (c) 2011-2015:  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__load_balancing_impl__
#define __H__UG__load_balancing_impl__
 
#include <vector>
#include "load_balancing.h"
#include "common/static_assert.h"
#include "lib_grid/algorithms/trees/kd_tree_static.h"
#include "lib_grid/algorithms/geom_obj_util/geom_obj_util.h"
 
namespace ug
{
 
 
template <class TElem, class TIterator, class TAAPos>
bool PartitionElements_RegularGrid(SubsetHandler& shOut,
                TIterator begin, TIterator end,
                int numCellsX, int numCellsY, int numCellsZ,
                TAAPos& aaPos,
                typename Grid::traits<TElem>::callback cbConsiderElem,
                int bucketSubset)
{
  using namespace ug;
  using namespace std;
 
  typedef typename TAAPos::ValueType vector_t;
 
//  make sure that the dimension is right
  UG_STATIC_ASSERT(TAAPos::ValueType::Size >= 2,
          TAPosition_has_to_be_at_least_two_dimensional);
 
  UG_ASSERT(shOut.grid(), "A grid has to be associated with the "
                      "specified subset handler.");
 
  if((numCellsX < 1) || (numCellsY < 1) || (numCellsZ < 1)){
    UG_THROW("At least one cell per direction should be specified.");
  }
 
  Grid& grid = *shOut.grid();
 
//  collect all elements which shall be considered for partitioning.
//  All others are assigned to bucketSubset
  vector<TElem*> elems;
  for(TIterator iter = begin; iter != end; ++iter){
    if(cbConsiderElem(*iter))
      elems.push_back(*iter);
    else
      shOut.assign_subset(*iter, bucketSubset);
  }
 
//  calculate the bounding box
  vector_t tmin(0), tmax(0);
  {
    grid.begin_marking();
    vector<Vertex*> vrts, associatedVrts;
    for(TIterator iter = begin; iter != end; ++iter){
      CollectAssociated(vrts, grid, *iter);
      for(size_t i = 0; i < vrts.size(); ++i){
        if(!grid.is_marked(vrts[i])){
          associatedVrts.push_back(vrts[i]);
          grid.mark(vrts[i]);
        }
      }
    }
    grid.end_marking();
 
    CalculateBoundingBox(tmin, tmax, associatedVrts.begin(),
               associatedVrts.end(), aaPos);
  }
 
  vector3 min, max;
  VecCopy(min, tmin, 0);
  VecCopy(max, tmax, 0);
 
  number width = max.x() - min.x();
  number height = max.y() - min.y();
  number depth = max.z() - min.z();
 
  if((width < SMALL) && numCellsX > 1){
    UG_LOG("Can't execute PartitionElements_Rectangle: Geometry has no width.\n");
    return false;
  }
  if((height < SMALL) && numCellsY > 1){
    UG_LOG("Can't execute PartitionElements_Rectangle: Geometry has no height.\n");
    return false;
  }
  if((depth < SMALL) && numCellsZ > 1){
    UG_LOG("Can't execute PartitionElements_Rectangle: Geometry has no height.\n");
    return false;
  }
 
 
//  iterate over all elements and calculate the index at which they shall be
//  inserted into the subset handler
  for(typename vector<TElem*>::iterator iter = elems.begin();
    iter != elems.end(); ++iter)
  {
    TElem* elem = *iter;
    vector3 center;
    VecCopy(center, CalculateCenter(elem, aaPos), 0);
 
  //  get the cell index
    int xInd = 0;
    if(numCellsX > 1)
        xInd = (int)((number)numCellsX * (center.x() - min.x()) / width);
    int yInd = 0;
    if(numCellsY > 1)
      yInd = (int)((number)numCellsY * (center.y() - min.y()) / height);
    int zInd = 0;
    if(numCellsZ > 1)
      zInd = (int)((number)numCellsZ * (center.z() - min.z()) / depth);
 
  //  calculate the subset index (one could think of several alternatives here)
    int si = zInd * numCellsX * numCellsY + yInd * numCellsX + xInd;
 
  //  assign the subset
    shOut.assign_subset(elem, si);
  }
  return true;
}
}// end of namespace
 
#endif
 
 
 
 
 
 
 
//  This is some old and unmaintained code.
//  Maybe it will be useful somewhen...
/*
template <class TElem, int IDimension>
bool PartitionElementsByRepeatedIntersectionKD(ug::SubsetHandler& shOut,
                    ug::Grid& grid,
                    int numSubsets,
                    ug::APosition& aVrtPos)
{
//  TODO: move implementation to separate ..._impl.hpp file.
  using namespace ug;
  using namespace std;
 
  typedef KDTreeStatic<APosition, IDimension> KDTree;
  typedef typename geometry_traits<TElem>::iterator ElemIterator;
 
//  get the max-size from the number of subsets that shall be constructed
  int treeDepth = 0;
  int numLeafs = 1;
  while(numLeafs < numSubsets)
  {
    treeDepth++;
    numLeafs *= 2;
  }
 
  if(numLeafs != numSubsets)
  {
    LOG("PROBLEM in PartitionElementsByRepeatedIntersection: ");
    LOG("numSubsets has to be chosen as a power of 2)\n");
    return false;
  }
 
//  fill a kd-tree with the vertices. This will help to find the elem-partition later on.
  KDTree kdTree;
  kdTree.create_from_grid(grid, grid.vertices_begin(), grid.vertices_end(),
            aVrtPos, treeDepth, 1, KDSD_CIRCULAR);
 
//  get the leafs
  vector<typename KDTree::Node*> vLeafs;
  kdTree.get_leafs(vLeafs);
 
  if(vLeafs.size() != numLeafs)
  {
  //  the algorithm failed, since it is not suited to deal with the
  //  given grid and the given parameters.
  //  You could try to distribute your grid onto less processes.
  //  The problem is, that the amount of vertices on both sides of a cut
  //  is not the same. This could be improved, by not choosing the cut-plane
  //  in the kd-tree in a geometric way, but by choosing it so, that
  //  the amount of vertices on both sides equals.
  //  To avoid this problem you could try to rotate your grid. Try to align it
  //  with the x, y and z axis - or write a better algorithm! This one is only
  //  suited for simple test-problems!!!
    LOG("PROBLEM in PartitionElementsByRepeatedIntersection: ");
    LOG("could not find the correct intersections.\n");
    LOG("This can happen depending on the properties of the grid.\n");
    LOG("Search the source-code for more informations.\n");
    return false;
  }
 
  shOut.clear();
 
//  we need a vertex-selector
  VertexSelector sel(grid);
 
//  iterate through the leafs. They are sorted in a special way.
  for(uint i = 0; i < vLeafs.size(); ++i)
  {
  //  select all vertices of the leaf.
    sel.select(vLeafs[i]->m_pvVertices->begin(), vLeafs[i]->m_pvVertices->end());
 
  //  now iterate through the elements of the grid.
    for(ElemIterator iter = grid.begin<TElem>(); iter != grid.end<TElem>(); ++iter)
    {
    //  push all elements that do not reference unselected vertices into the i-th subset.
    //  all elements will be assigned to a subset this way, since all vertices are
    //  selected in the last iteration.
      TElem* ele = *iter;
    //  make sure, that the element is not already assigned to a subset.
      if(shOut.get_subset_index(ele) == -1)
      {
        bool bAllSelected = true;
        for(int j = 0; j < ele->num_vertices(); ++j)
        {
          if(!sel.is_selected(ele->vertex(j)))
          {
            bAllSelected = false;
            break;
          }
        }
 
      //  if all vertices were selected, we'll push the element to the subset.
        if(bAllSelected)
          shOut.assign_subset(ele, i);
      }
    }
  }
 
//TODO: exchange elements between subsets until all subsets meet a certain criterion.
 
  return true;
}
*/