meshGenUtils.h

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// ---------------------------------------------------------------------
//
// Copyright (c) 2017-2025 The Regents of the University of Michigan and DFT-FE
// authors.
//
// This file is part of the DFT-FE code.
//
// The DFT-FE code is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the DFT-FE distribution.
//
// ---------------------------------------------------------------------
//
// @author Sambit Das, Phani Motamarri
//
 
#ifndef meshGenUtils_H_
#define meshGenUtils_H_
 
#include <headers.h>
#include "dftParameters.h"
 
namespace dftfe
{
  namespace meshGenUtils
  {
    inline void
    cross_product(std::vector<double> &a,
                  std::vector<double> &b,
                  std::vector<double> &crossProduct)
    {
      crossProduct.resize(a.size(), 0.0);
 
      crossProduct[0] = a[1] * b[2] - a[2] * b[1];
      crossProduct[1] = a[2] * b[0] - a[0] * b[2];
      crossProduct[2] = a[0] * b[1] - a[1] * b[0];
    }
 
    inline void
    computePeriodicFaceNormals(
      std::vector<std::vector<double>> &latticeVectors,
      std::vector<std::vector<double>> &periodicFaceNormals)
    {
      // resize periodic face normal
      periodicFaceNormals.resize(3);
 
 
      // evaluate cross product between first two lattice vectors
      cross_product(latticeVectors[0],
                    latticeVectors[1],
                    periodicFaceNormals[2]);
 
      // evaluate cross product between second two lattice vectors
      cross_product(latticeVectors[1],
                    latticeVectors[2],
                    periodicFaceNormals[0]);
 
 
      // evaluate cross product between third and first two lattice vectors
      cross_product(latticeVectors[2],
                    latticeVectors[0],
                    periodicFaceNormals[1]);
    }
 
    inline void
    computeOffsetVectors(std::vector<std::vector<double>>  &latticeVectors,
                         std::vector<dealii::Tensor<1, 3>> &offsetVectors)
    {
      // create unitVectorsXYZ
      std::vector<std::vector<double>> unitVectorsXYZ;
      unitVectorsXYZ.resize(3);
 
      for (dftfe::Int i = 0; i < 3; ++i)
        {
          unitVectorsXYZ[i].resize(3, 0.0);
          unitVectorsXYZ[i][i] = 0.0;
        }
 
 
      // resize offset vectors
      offsetVectors.resize(3);
 
      for (dftfe::Int i = 0; i < 3; ++i)
        {
          for (dftfe::Int j = 0; j < 3; ++j)
            {
              offsetVectors[i][j] = unitVectorsXYZ[i][j] - latticeVectors[i][j];
            }
        }
    }
 
 
    inline double
    getCosineAngle(dealii::Tensor<1, 3> &Vector1, std::vector<double> &Vector2)
    {
      double dotProduct = Vector1[0] * Vector2[0] + Vector1[1] * Vector2[1] +
                          Vector1[2] * Vector2[2];
      double lengthVector1Sq =
        (Vector1[0] * Vector1[0] + Vector1[1] * Vector1[1] +
         Vector1[2] * Vector1[2]);
      double lengthVector2Sq =
        (Vector2[0] * Vector2[0] + Vector2[1] * Vector2[1] +
         Vector2[2] * Vector2[2]);
 
      double angle = dotProduct / sqrt(lengthVector1Sq * lengthVector2Sq);
 
      return angle;
    }
 
 
    inline double
    getCosineAngle(std::vector<double> &Vector1, std::vector<double> &Vector2)
    {
      double dotProduct = Vector1[0] * Vector2[0] + Vector1[1] * Vector2[1] +
                          Vector1[2] * Vector2[2];
      double lengthVector1Sq =
        (Vector1[0] * Vector1[0] + Vector1[1] * Vector1[1] +
         Vector1[2] * Vector1[2]);
      double lengthVector2Sq =
        (Vector2[0] * Vector2[0] + Vector2[1] * Vector2[1] +
         Vector2[2] * Vector2[2]);
 
      double angle = dotProduct / sqrt(lengthVector1Sq * lengthVector2Sq);
 
      return angle;
    }
 
 
    inline void
    markPeriodicFacesNonOrthogonal(
      dealii::Triangulation<3, 3>      &triangulation,
      std::vector<std::vector<double>> &latticeVectors,
      const MPI_Comm                   &mpiCommParent,
      const dftParameters              &dftParams)
    {
      dealii::ConditionalOStream pcout(
        std::cout,
        (dealii::Utilities::MPI::this_mpi_process(mpiCommParent) == 0));
      std::vector<std::vector<double>>  periodicFaceNormals;
      std::vector<dealii::Tensor<1, 3>> offsetVectors;
      // bool periodicX = dftParameters::periodicX, periodicY =
      // dftParameters::periodicY, periodicZ=dftParameters::periodicZ;
 
      // compute periodic face normals from lattice vector information
      computePeriodicFaceNormals(latticeVectors, periodicFaceNormals);
 
      // compute offset vectors such that lattice vectors plus offset vectors
      // are alligned along spatial x,y,z directions
      computeOffsetVectors(latticeVectors, offsetVectors);
 
      if (dftParams.verbosity >= 4)
        {
          pcout << "Periodic Face Normals 1: " << periodicFaceNormals[0][0]
                << " " << periodicFaceNormals[0][1] << " "
                << periodicFaceNormals[0][2] << std::endl;
          pcout << "Periodic Face Normals 2: " << periodicFaceNormals[1][0]
                << " " << periodicFaceNormals[1][1] << " "
                << periodicFaceNormals[1][2] << std::endl;
          pcout << "Periodic Face Normals 3: " << periodicFaceNormals[2][0]
                << " " << periodicFaceNormals[2][1] << " "
                << periodicFaceNormals[2][2] << std::endl;
        }
 
      dealii::QGauss<2>   quadratureFace_formula(2);
      dealii::FESystem<3> FE(dealii::FE_Q<3>(dealii::QGaussLobatto<1>(2)), 1);
      dealii::FEFaceValues<3> feFace_values(FE,
                                            quadratureFace_formula,
                                            dealii::update_normal_vectors);
 
      typename dealii::Triangulation<3, 3>::active_cell_iterator cell, endc;
      //
      // mark faces
      //
      // const dftfe::uInt px=dftParameters::periodicX,
      // py=dftParameters::periodicX, pz=dftParameters::periodicX;
      //
      cell = triangulation.begin_active(), endc = triangulation.end();
      const std::array<dftfe::Int, 3> periodic = {dftParams.periodicX,
                                                  dftParams.periodicY,
                                                  dftParams.periodicZ};
      for (; cell != endc; ++cell)
        {
          for (dftfe::uInt f = 0; f < dealii::GeometryInfo<3>::faces_per_cell;
               ++f)
            {
              const dealii::Point<3> face_center = cell->face(f)->center();
              if (cell->face(f)->at_boundary())
                {
                  feFace_values.reinit(cell, f);
                  dealii::Tensor<1, 3> faceNormalVector =
                    feFace_values.normal_vector(0);
 
                  // std::cout<<"Face normal vector: "<<faceNormalVector[0]<<"
                  // "<<faceNormalVector[1]<<"
                  // "<<faceNormalVector[2]<<std::endl; pcout<<"Angle :
                  // "<<getCosineAngle(faceNormalVector,periodicFaceNormals[0])<<"
                  // "<<getCosineAngle(faceNormalVector,periodicFaceNormals[1])<<"
                  // "<<getCosineAngle(faceNormalVector,periodicFaceNormals[2])<<std::endl;
 
                  dftfe::uInt i = 1;
 
                  for (dftfe::uInt d = 0; d < 3; ++d)
                    {
                      if (periodic[d] == 1)
                        {
                          if (std::abs(getCosineAngle(faceNormalVector,
                                                      periodicFaceNormals[d]) -
                                       1.0) < 1.0e-05)
                            cell->face(f)->set_boundary_id(i);
                          else if (std::abs(
                                     getCosineAngle(faceNormalVector,
                                                    periodicFaceNormals[d]) +
                                     1.0) < 1.0e-05)
                            cell->face(f)->set_boundary_id(i + 1);
                          i = i + 2;
                        }
                    }
                }
            }
        }
 
      std::vector<dftfe::Int> periodicDirectionVector;
 
      for (dftfe::uInt d = 0; d < 3; ++d)
        {
          if (periodic[d] == 1)
            {
              periodicDirectionVector.push_back(d);
            }
        }
 
      // pcout << "Done with Boundary Flags\n";
      std::vector<dealii::GridTools::PeriodicFacePair<
        typename dealii::Triangulation<3, 3>::cell_iterator>>
        periodicity_vector;
      for (dftfe::Int i = 0;
           i < std::accumulate(periodic.begin(), periodic.end(), 0);
           ++i)
        {
          dealii::GridTools::collect_periodic_faces(
            triangulation,
            /*b_id1*/ 2 * i + 1,
            /*b_id2*/ 2 * i + 2,
            /*direction*/ periodicDirectionVector[i],
            periodicity_vector,
            offsetVectors[periodicDirectionVector[i]]);
          // dealii::GridTools::collect_periodic_faces(triangulation, /*b_id1*/
          // 2*i+1,
          // /*b_id2*/ 2*i+2,/*direction*/ i, periodicity_vector);
        }
      triangulation.add_periodicity(periodicity_vector);
 
      if (dftParams.verbosity >= 4)
        pcout << "Periodic Facepairs size: " << periodicity_vector.size()
              << std::endl;
      /*
         for(dftfe::uInt i=0; i< periodicity_vector.size(); ++i)
         {
         if (!periodicity_vector[i].cell[0]->active() ||
         !periodicity_vector[i].cell[1]->active()) continue; if
         (periodicity_vector[i].cell[0]->is_artificial() ||
         periodicity_vector[i].cell[1]->is_artificial()) continue;
 
         std::cout << "matched face pairs: "<<
         periodicity_vector[i].cell[0]->face(periodicity_vector[i].face_idx[0])->boundary_id()
         << " "<<
         periodicity_vector[i].cell[1]->face(periodicity_vector[i].face_idx[1])->boundary_id()<<std::endl;
         }
       */
    }
 
  } // namespace meshGenUtils
} // namespace dftfe
#endif