C++ MeshBase::active_pid_elements_end方法代码示例

void ParmetisPartitioner::initialize (const MeshBase & mesh,
                                      const unsigned int n_sbdmns)
{
  const dof_id_type n_active_local_elem = mesh.n_active_local_elem();

  // Set parameters.
  _pmetis->wgtflag = 2;                                      // weights on vertices only
  _pmetis->ncon    = 1;                                      // one weight per vertex
  _pmetis->numflag = 0;                                      // C-style 0-based numbering
  _pmetis->nparts  = static_cast<Parmetis::idx_t>(n_sbdmns); // number of subdomains to create
  _pmetis->edgecut = 0;                                      // the numbers of edges cut by the
                                                             // partition

  // Initialize data structures for ParMETIS
  _pmetis->vtxdist.resize (mesh.n_processors()+1); std::fill (_pmetis->vtxdist.begin(), _pmetis->vtxdist.end(), 0);
  _pmetis->tpwgts.resize  (_pmetis->nparts);       std::fill (_pmetis->tpwgts.begin(),  _pmetis->tpwgts.end(),  1./_pmetis->nparts);
  _pmetis->ubvec.resize   (_pmetis->ncon);         std::fill (_pmetis->ubvec.begin(),   _pmetis->ubvec.end(),   1.05);
  _pmetis->part.resize    (n_active_local_elem);   std::fill (_pmetis->part.begin(),    _pmetis->part.end(), 0);
  _pmetis->options.resize (5);
  _pmetis->vwgt.resize    (n_active_local_elem);

  // Set the options
  _pmetis->options[0] = 1;  // don't use default options
  _pmetis->options[1] = 0;  // default (level of timing)
  _pmetis->options[2] = 15; // random seed (default)
  _pmetis->options[3] = 2;  // processor distribution and subdomain distribution are decoupled

  // Find the number of active elements on each processor.  We cannot use
  // mesh.n_active_elem_on_proc(pid) since that only returns the number of
  // elements assigned to pid which are currently stored on the calling
  // processor. This will not in general be correct for parallel meshes
  // when (pid!=mesh.processor_id()).
  _n_active_elem_on_proc.resize(mesh.n_processors());
  mesh.comm().allgather(n_active_local_elem, _n_active_elem_on_proc);

  // count the total number of active elements in the mesh.  Note we cannot
  // use mesh.n_active_elem() in general since this only returns the number
  // of active elements which are stored on the calling processor.
  // We should not use n_active_elem for any allocation because that will
  // be inheritly unscalable, but it can be useful for libmesh_assertions.
  dof_id_type n_active_elem=0;

  // Set up the vtxdist array.  This will be the same on each processor.
  // ***** Consult the Parmetis documentation. *****
  libmesh_assert_equal_to (_pmetis->vtxdist.size(),
                           cast_int<std::size_t>(mesh.n_processors()+1));
  libmesh_assert_equal_to (_pmetis->vtxdist[0], 0);

  for (processor_id_type pid=0; pid<mesh.n_processors(); pid++)
    {
      _pmetis->vtxdist[pid+1] = _pmetis->vtxdist[pid] + _n_active_elem_on_proc[pid];
      n_active_elem += _n_active_elem_on_proc[pid];
    }
  libmesh_assert_equal_to (_pmetis->vtxdist.back(), static_cast<Parmetis::idx_t>(n_active_elem));

  // ParMetis expects the elements to be numbered in contiguous blocks
  // by processor, i.e. [0, ne0), [ne0, ne0+ne1), ...
  // Since we only partition active elements we should have no expectation
  // that we currently have such a distribution.  So we need to create it.
  // Also, at the same time we are going to map all the active elements into a globally
  // unique range [0,n_active_elem) which is *independent* of the current partitioning.
  // This can be fed to ParMetis as the initial partitioning of the subdomains (decoupled
  // from the partitioning of the objects themselves).  This allows us to get the same
  // resultant partitioning independed of the input partitioning.
  MeshTools::BoundingBox bbox =
    MeshTools::bounding_box(mesh);

  _global_index_by_pid_map.clear();

  // Maps active element ids into a contiguous range independent of partitioning.
  // (only needs local scope)
  vectormap<dof_id_type, dof_id_type> global_index_map;

  {
    std::vector<dof_id_type> global_index;

    // create the mapping which is contiguous by processor
    dof_id_type pid_offset=0;
    for (processor_id_type pid=0; pid<mesh.n_processors(); pid++)
      {
        MeshBase::const_element_iterator       it  = mesh.active_pid_elements_begin(pid);
        const MeshBase::const_element_iterator end = mesh.active_pid_elements_end(pid);

        // note that we may not have all (or any!) the active elements which belong on this processor,
        // but by calling this on all processors a unique range in [0,_n_active_elem_on_proc[pid])
        // is constructed.  Only the indices for the elements we pass in are returned in the array.
        MeshCommunication().find_global_indices (mesh.comm(),
                                                 bbox, it, end,
                                                 global_index);

        for (dof_id_type cnt=0; it != end; ++it)
          {
            const Elem * elem = *it;
            libmesh_assert (!_global_index_by_pid_map.count(elem->id()));
            libmesh_assert_less (cnt, global_index.size());
            libmesh_assert_less (global_index[cnt], _n_active_elem_on_proc[pid]);

            _global_index_by_pid_map.insert(std::make_pair(elem->id(), global_index[cnt++] + pid_offset));
          }

//.........这里部分代码省略.........