meshcolorizer.hpp

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//==============================================================================
//==============================================================================

#ifndef MESHCOLORIZER_HPP_
#define MESHCOLORIZER_HPP_

#include <vector>

  template<class GridType>
class MeshColorizer {
  typedef std::vector<int> IntVec; 
  typedef std::vector<IntVec> IntMat; 

  public:
    explicit MeshColorizer(const GridType& grid_) :
      grid(grid_)
    {
      calcGroups();
    }

    const IntMat& operator[](unsigned int i)
    {
      return tg[i];
    }

    void calcGroups()
    {
      tg[0].resize(1);
      tg[0].reserve(grid.size(0));
      for (int i = 0; i < grid.size(0); ++i) {
        tg[0][0].push_back(i);
      }
      tg[1].clear();
    }

  private:
    IntMat tg[2]; 
    const GridType& grid; 

    int getStripDirection (int nel1, int nel2, int nel3, int parts)
    {
      int s1 = nel1 / parts;
      int s2 = nel2 / parts;
      int s3 = nel3 / parts;
      int r1 = nel1 - s1*parts;
      int r2 = nel2 - s2*parts;
      int r3 = nel3 - s3*parts;

      if (r1*nel2*nel3 < nel1*r2*nel3 && r1*nel2*nel3 < nel1*nel2*r3)
        return 0; // strips along x axis
      else if (nel1*r2*nel3 < r1*nel2*nel3 && nel1*r2*nel3 < nel1*nel2*r3)
        return 1; // strips along y axis
      else if (nel1*nel2*r3 < r1*nel2*nel3 && nel1*nel2*r3 < nel1*r2*nel3)
        return 2; // strips along z axis

      // The number of left-over elements is not smallest in one direction only
      if (r1*nel2*nel3 > nel1*r2*nel3)
        return nel2 > nel3 ? 1 : 2;
      else if (nel1*r2*nel3 > nel1*nel2*r3)
        return nel1 > nel3 ? 0 : 2;
      else if (nel1*nel2*r3 > r1*nel2*nel3)
        return nel1 > nel2 ? 0 : 1;

      // The number of left-over elements is the same in all three directions
      if (nel1 >= nel2 && nel1 >= nel3)
        return 0;
      else if (nel2 >= nel1 && nel2 >= nel3)
        return 1;
      else
        return 2;
    }
};

#endif