libMesh::MappedSubdomainPartitioner Class Reference

The MappedSubdomainPartitioner partitions the elements based on their subdomain ids. More...

#include <mapped_subdomain_partitioner.h>

Inheritance diagram for libMesh::MappedSubdomainPartitioner:

Public Member Functions
	MappedSubdomainPartitioner ()=default
	Ctors, assignment operators, and destructor are all explicitly defaulted for this class. More...
	MappedSubdomainPartitioner (const MappedSubdomainPartitioner &)=default
	MappedSubdomainPartitioner (MappedSubdomainPartitioner &&)=default
MappedSubdomainPartitioner &	operator= (const MappedSubdomainPartitioner &)=default
MappedSubdomainPartitioner &	operator= (MappedSubdomainPartitioner &&)=default
virtual	~MappedSubdomainPartitioner ()=default
virtual PartitionerType	type () const override
virtual std::unique_ptr< Partitioner >	clone () const override
virtual void	partition_range (MeshBase &mesh, MeshBase::element_iterator it, MeshBase::element_iterator end, const unsigned int n) override
	Called by the SubdomainPartitioner to partition elements in the range (it, end). More...
virtual void	partition (MeshBase &mesh, const unsigned int n)
	Partitions the MeshBase into n parts by setting processor_id() on Nodes and Elems. More...
virtual void	partition (MeshBase &mesh)
	Partitions the MeshBase into mesh.n_processors() by setting processor_id() on Nodes and Elems. More...
void	repartition (MeshBase &mesh, const unsigned int n)
	Repartitions the MeshBase into n parts. More...
void	repartition (MeshBase &mesh)
	Repartitions the MeshBase into mesh.n_processors() parts. More...
virtual void	attach_weights (ErrorVector *)
	Attach weights that can be used for partitioning. More...

Static Public Member Functions
static std::unique_ptr< Partitioner >	build (const PartitionerType solver_package)
	Builds a Partitioner of the type specified by partitioner_type. More...
static void	partition_unpartitioned_elements (MeshBase &mesh)
	These functions assign processor IDs to newly-created elements (in parallel) which are currently assigned to processor 0. More...
static void	partition_unpartitioned_elements (MeshBase &mesh, const unsigned int n)
static void	set_parent_processor_ids (MeshBase &mesh)
	This function is called after partitioning to set the processor IDs for the inactive parent elements. More...
static void	set_node_processor_ids (MeshBase &mesh)
	This function is called after partitioning to set the processor IDs for the nodes. More...
static void	processor_pairs_to_interface_nodes (MeshBase &mesh, std::map< std::pair< processor_id_type, processor_id_type >, std::set< dof_id_type >> &processor_pair_to_nodes)
	On the partitioning interface, a surface is shared by two and only two processors. More...
static void	set_interface_node_processor_ids_linear (MeshBase &mesh)
	Nodes on the partitioning interface is linearly assigned to each pair of processors. More...
static void	set_interface_node_processor_ids_BFS (MeshBase &mesh)
	Nodes on the partitioning interface is clustered into two groups BFS (Breadth First Search)scheme for per pair of processors. More...
static void	set_interface_node_processor_ids_petscpartitioner (MeshBase &mesh)
	Nodes on the partitioning interface is partitioned into two groups using a PETSc partitioner for each pair of processors. More...

Public Attributes
std::map< subdomain_id_type, processor_id_type >	subdomain_to_proc
	Before calling partition() or partition_range(), the user must assign all the Mesh subdomains to certain processors by adding them to this std::map. More...

Protected Member Functions
virtual void	_do_partition (MeshBase &mesh, const unsigned int n) override
	Partition the MeshBase into n subdomains. More...
bool	single_partition (MeshBase &mesh)
	Trivially "partitions" the mesh for one processor. More...
bool	single_partition_range (MeshBase::element_iterator it, MeshBase::element_iterator end)
	Slightly generalized version of single_partition which acts on a range of elements defined by the pair of iterators (it, end). More...
virtual void	_do_repartition (MeshBase &mesh, const unsigned int n)
	This is the actual re-partitioning method which can be overridden in derived classes. More...
virtual void	_find_global_index_by_pid_map (const MeshBase &mesh)
	Construct contiguous global indices for the current partitioning. More...
virtual void	build_graph (const MeshBase &mesh)
	Build a dual graph for partitioner. More...
void	assign_partitioning (MeshBase &mesh, const std::vector< dof_id_type > &parts)
	Assign the computed partitioning to the mesh. More...

Protected Attributes
ErrorVector *	_weights
	The weights that might be used for partitioning. More...
std::unordered_map< dof_id_type, dof_id_type >	_global_index_by_pid_map
	Maps active element ids into a contiguous range, as needed by parallel partitioner. More...
std::vector< dof_id_type >	_n_active_elem_on_proc
	The number of active elements on each processor. More...
std::vector< std::vector< dof_id_type > >	_dual_graph
	A dual graph corresponds to the mesh, and it is typically used in paritioner. More...
std::vector< Elem * >	_local_id_to_elem

Static Protected Attributes
static const dof_id_type	communication_blocksize
	The blocksize to use when doing blocked parallel communication. More...

Detailed Description

The MappedSubdomainPartitioner partitions the elements based on their subdomain ids.

The user must set up the values in the public subdomain_to_proc map in order to specify which subdomains should be partitioned onto which processors. More than one subdomain can be partitioned onto a given processor, but every subdomain must be assigned to exactly 1 processor.

Author

John W. Peterson

Date

2017 Partitions elements based on user-defined mapping from subdomain ids -> processor ids.

Definition at line 44 of file mapped_subdomain_partitioner.h.

Constructor & Destructor Documentation

MappedSubdomainPartitioner() [1/3]

libMesh::MappedSubdomainPartitioner::MappedSubdomainPartitioner ( )

default

Ctors, assignment operators, and destructor are all explicitly defaulted for this class.

MappedSubdomainPartitioner() [2/3]

libMesh::MappedSubdomainPartitioner::MappedSubdomainPartitioner ( const MappedSubdomainPartitioner &  )

default

MappedSubdomainPartitioner() [3/3]

libMesh::MappedSubdomainPartitioner::MappedSubdomainPartitioner ( MappedSubdomainPartitioner &&  )

default

~MappedSubdomainPartitioner()

virtual libMesh::MappedSubdomainPartitioner::~MappedSubdomainPartitioner ( )

virtualdefault

Member Function Documentation

_do_partition()

void libMesh::MappedSubdomainPartitioner::_do_partition ( MeshBase &  mesh, const unsigned int  n  )

overrideprotectedvirtual

Partition the MeshBase into n subdomains.

Implements libMesh::Partitioner.

Definition at line 67 of file mapped_subdomain_partitioner.C.

References mesh, and partition_range().

{
  this->partition_range(mesh,
                        mesh.active_elements_begin(),
                        mesh.active_elements_end(),
                        n);
}

_do_repartition()

virtual void libMesh::Partitioner::_do_repartition ( MeshBase &  mesh, const unsigned int  n  )

inlineprotectedvirtualinherited

This is the actual re-partitioning method which can be overridden in derived classes.

Note

The default behavior is to simply call the partition function.

Reimplemented in libMesh::ParmetisPartitioner.

Definition at line 251 of file partitioner.h.

References libMesh::Partitioner::_do_partition().

Referenced by libMesh::Partitioner::repartition().

                                                      { this->_do_partition (mesh, n); }

_find_global_index_by_pid_map()

void libMesh::Partitioner::_find_global_index_by_pid_map ( const MeshBase &  mesh )

protectedvirtualinherited

Construct contiguous global indices for the current partitioning.

The global indices are ordered part-by-part

Definition at line 1068 of file partitioner.C.

References libMesh::Partitioner::_global_index_by_pid_map, libMesh::Partitioner::_n_active_elem_on_proc, TIMPI::Communicator::allgather(), libMesh::ParallelObject::comm(), libMesh::MeshTools::create_bounding_box(), libMesh::MeshCommunication::find_local_indices(), libMesh::make_range(), mesh, libMesh::MeshBase::n_active_local_elem(), libMesh::ParallelObject::n_processors(), and libMesh::Parallel::sync_dofobject_data_by_id().

Referenced by libMesh::Partitioner::build_graph().

{
  const dof_id_type n_active_local_elem = mesh.n_active_local_elem();

  // 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()).
  auto n_proc = mesh.n_processors();
  _n_active_elem_on_proc.resize(n_proc);
  mesh.comm().allgather(n_active_local_elem, _n_active_elem_on_proc);

  std::vector<dof_id_type> n_active_elem_before_proc(mesh.n_processors());

  for (auto i : make_range(n_proc-1))
    n_active_elem_before_proc[i+1] =
      n_active_elem_before_proc[i] + _n_active_elem_on_proc[i];

  libMesh::BoundingBox bbox =
    MeshTools::create_bounding_box(mesh);

  _global_index_by_pid_map.clear();

  // create the mapping which is contiguous by processor
  MeshCommunication().find_local_indices (bbox,
                                          mesh.active_local_elements_begin(),
                                          mesh.active_local_elements_end(),
                                          _global_index_by_pid_map);

  SyncLocalIDs sync(_global_index_by_pid_map);

  Parallel::sync_dofobject_data_by_id
      (mesh.comm(), mesh.active_elements_begin(), mesh.active_elements_end(), sync);

  for (const auto & elem : mesh.active_element_ptr_range())
    {
      const processor_id_type pid = elem->processor_id();
      libmesh_assert_less (_global_index_by_pid_map[elem->id()], _n_active_elem_on_proc[pid]);

      _global_index_by_pid_map[elem->id()] += n_active_elem_before_proc[pid];
    }
}

assign_partitioning()

void libMesh::Partitioner::assign_partitioning ( MeshBase &  mesh, const std::vector< dof_id_type > &  parts  )

protectedinherited

Assign the computed partitioning to the mesh.

Definition at line 1467 of file partitioner.C.

References libMesh::Partitioner::_global_index_by_pid_map, libMesh::Partitioner::_n_active_elem_on_proc, libMesh::ParallelObject::comm(), libMesh::libmesh_assert(), libMesh::make_range(), mesh, libMesh::MeshBase::n_active_local_elem(), libMesh::MeshBase::n_partitions(), libMesh::ParallelObject::n_processors(), and libMesh::ParallelObject::processor_id().

{
  LOG_SCOPE("assign_partitioning()", "Partitioner");

  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

  dof_id_type first_local_elem = 0;
  for (auto pid : make_range(mesh.processor_id()))
    first_local_elem += _n_active_elem_on_proc[pid];

#ifndef NDEBUG
  const dof_id_type n_active_local_elem = mesh.n_active_local_elem();
#endif

  std::map<processor_id_type, std::vector<dof_id_type>>
    requested_ids;

  // Results to gather from each processor - kept in a map so we
  // do only one loop over elements after all receives are done.
  std::map<processor_id_type, std::vector<processor_id_type>>
    filled_request;

  for (auto & elem : mesh.active_element_ptr_range())
    {
      // we need to get the index from the owning processor
      // (note we cannot assign it now -- we are iterating
      // over elements again and this will be bad!)
      requested_ids[elem->processor_id()].push_back(elem->id());
    }

  auto gather_functor =
    [this,
     & parts,
#ifndef NDEBUG
     & mesh,
     n_active_local_elem,
#endif
     first_local_elem]
    (processor_id_type, const std::vector<dof_id_type> & ids,
     std::vector<processor_id_type> & data)
    {
      const std::size_t ids_size = ids.size();
      data.resize(ids.size());

      for (std::size_t i=0; i != ids_size; i++)
        {
          const dof_id_type requested_elem_index = ids[i];

          libmesh_assert(_global_index_by_pid_map.count(requested_elem_index));

          const dof_id_type global_index_by_pid =
            _global_index_by_pid_map[requested_elem_index];

          const dof_id_type local_index =
            global_index_by_pid - first_local_elem;

          libmesh_assert_less (local_index, parts.size());
          libmesh_assert_less (local_index, n_active_local_elem);

          const processor_id_type elem_procid =
            cast_int<processor_id_type>(parts[local_index]);

          libmesh_assert_less (elem_procid, mesh.n_partitions());

          data[i] = elem_procid;
        }
    };

  auto action_functor =
    [&filled_request]
    (processor_id_type pid,
     const std::vector<dof_id_type> &,
     const std::vector<processor_id_type> & new_procids)
    {
      filled_request[pid] = new_procids;
    };

  // Trade requests with other processors
  const processor_id_type * ex = nullptr;
  Parallel::pull_parallel_vector_data
    (mesh.comm(), requested_ids, gather_functor, action_functor, ex);

  // and finally assign the partitioning.
  // note we are iterating in exactly the same order
  // used to build up the request, so we can expect the
  // required entries to be in the proper sequence.
  std::vector<unsigned int> counters(mesh.n_processors(), 0);
  for (auto & elem : mesh.active_element_ptr_range())
    {
      const processor_id_type current_pid = elem->processor_id();

      libmesh_assert_less (counters[current_pid], requested_ids[current_pid].size());

      const processor_id_type elem_procid =
        filled_request[current_pid][counters[current_pid]++];

      libmesh_assert_less (elem_procid, mesh.n_partitions());
      elem->processor_id() = elem_procid;
    }
}

attach_weights()

virtual void libMesh::Partitioner::attach_weights ( ErrorVector *  )

inlinevirtualinherited

Attach weights that can be used for partitioning.

This ErrorVector should be exactly the same on every processor and should have mesh->max_elem_id() entries.

Reimplemented in libMesh::MetisPartitioner.

Definition at line 213 of file partitioner.h.

{ libmesh_not_implemented(); }

build()

std::unique_ptr< Partitioner > libMesh::Partitioner::build ( const PartitionerType  solver_package )

staticinherited

Builds a Partitioner of the type specified by partitioner_type.

Definition at line 159 of file partitioner.C.

References libMesh::CENTROID_PARTITIONER, libMesh::Utility::enum_to_string(), libMesh::HILBERT_SFC_PARTITIONER, libMesh::LINEAR_PARTITIONER, libMesh::MAPPED_SUBDOMAIN_PARTITIONER, libMesh::METIS_PARTITIONER, libMesh::MORTON_SFC_PARTITIONER, libMesh::PARMETIS_PARTITIONER, libMesh::SFC_PARTITIONER, and libMesh::SUBDOMAIN_PARTITIONER.

Referenced by libMesh::DistributedMesh::DistributedMesh(), libMesh::ReplicatedMesh::ReplicatedMesh(), PartitionerTest< PartitionerSubclass, MeshClass >::testBuild(), and MeshDeletionsTest::testDeleteElem().

{
  switch (partitioner_type)
  {
    case CENTROID_PARTITIONER:
      return std::make_unique<CentroidPartitioner>();
    case LINEAR_PARTITIONER:
      return std::make_unique<LinearPartitioner>();
    case MAPPED_SUBDOMAIN_PARTITIONER:
      return std::make_unique<MappedSubdomainPartitioner>();
    case METIS_PARTITIONER:
      return std::make_unique<MetisPartitioner>();
    case PARMETIS_PARTITIONER:
      return std::make_unique<ParmetisPartitioner>();
    case HILBERT_SFC_PARTITIONER:
      return std::make_unique<HilbertSFCPartitioner>();
    case MORTON_SFC_PARTITIONER:
      return std::make_unique<MortonSFCPartitioner>();
    case SFC_PARTITIONER:
      return std::make_unique<SFCPartitioner>();
    case SUBDOMAIN_PARTITIONER:
      return std::make_unique<SubdomainPartitioner>();
    default:
      libmesh_error_msg("Invalid partitioner type: " <<
                        Utility::enum_to_string(partitioner_type));
  }
}

build_graph()

void libMesh::Partitioner::build_graph ( const MeshBase &  mesh )

protectedvirtualinherited

Build a dual graph for partitioner.

Reimplemented in libMesh::ParmetisPartitioner.

Definition at line 1112 of file partitioner.C.

References libMesh::Partitioner::_dual_graph, libMesh::Partitioner::_find_global_index_by_pid_map(), libMesh::Partitioner::_global_index_by_pid_map, libMesh::Partitioner::_local_id_to_elem, libMesh::Partitioner::_n_active_elem_on_proc, libMesh::as_range(), libMesh::ParallelObject::comm(), libMesh::MeshBase::get_constraint_rows(), libMesh::DofObject::id(), libMesh::index_range(), libMesh::libmesh_assert(), libMesh::libmesh_ignore(), libMesh::make_range(), TIMPI::Communicator::max(), mesh, libMesh::MeshBase::n_active_local_elem(), libMesh::ParallelObject::n_processors(), libMesh::ParallelObject::processor_id(), and libMesh::DofObject::processor_id().

{
  LOG_SCOPE("build_graph()", "Partitioner");

  const dof_id_type n_active_local_elem  = mesh.n_active_local_elem();

  // If we have boundary elements in this mesh, we want to account for
  // the connectivity between them and interior elements.  We can find
  // interior elements from boundary elements, but we need to build up
  // a lookup map to do the reverse.
  typedef std::unordered_multimap<const Elem *, const Elem *> map_type;
  map_type interior_to_boundary_map;

  // If we have spline nodes in this mesh, we want to account for the
  // connectivity between them and integration elements.  We can find
  // spline nodes from integration elements, but need a reverse map
  // {integration_elements} = elems_constrained_by[spline_nodeelem]
  map_type elems_constrained_by;

  const auto & mesh_constrained_nodes = mesh.get_constraint_rows();

  for (const Elem * elem : mesh.active_element_ptr_range())
    {
      if (!mesh_constrained_nodes.empty()) // quick test for non-IGA cases
        {
          const auto end_it = mesh_constrained_nodes.end();

          // Use a set to avoid duplicates.  Use a well-defined method
          // of ordering that set to make debugging easier.
          std::set<const Elem *, CompareElemIdsByLevel> constraining_elems;
          for (const Node & node : elem->node_ref_range())
            {
              if (const auto row_it = mesh_constrained_nodes.find(&node);
                  row_it != end_it)
                for (const auto & [pr, coef] : row_it->second)
                  {
                    libmesh_ignore(coef); // avoid gcc 7 warning
                    constraining_elems.insert(pr.first);
                  }
            }
          for (const Elem * constraining_elem : constraining_elems)
            elems_constrained_by.emplace(constraining_elem, elem);
        }

      // If we don't have an interior_parent and we don't have any
      // constrained nodes then there's nothing else to look up.
      if (elem->interior_parent())
        {
          // get all relevant interior elements
          std::set<const Elem *> neighbor_set;
          elem->find_interior_neighbors(neighbor_set);

          for (const auto & neighbor : neighbor_set)
            interior_to_boundary_map.emplace(neighbor, elem);
        }
    }

#ifdef LIBMESH_ENABLE_AMR
  std::vector<const Elem *> neighbors_offspring;
#endif

  // This is costly, and we only need to do it if the mesh has
  // changed since we last partitioned... but the mesh probably has
  // changed since we last partitioned, and if it hasn't we don't
  // have a reliable way to be sure of that.
  _find_global_index_by_pid_map(mesh);

  dof_id_type first_local_elem = 0;
  for (auto pid : make_range(mesh.processor_id()))
     first_local_elem += _n_active_elem_on_proc[pid];

  _dual_graph.clear();
  _dual_graph.resize(n_active_local_elem);
  _local_id_to_elem.resize(n_active_local_elem);

  // We may need to communicate constraint-row-based connections
  // between processors
  std::unordered_map<processor_id_type,
    std::vector<std::pair<dof_id_type, dof_id_type>>> connections_to_push;

  for (const auto & elem : mesh.active_local_element_ptr_range())
    {
      libmesh_assert (_global_index_by_pid_map.count(elem->id()));
      const dof_id_type global_index_by_pid =
        _global_index_by_pid_map[elem->id()];

      const dof_id_type local_index =
        global_index_by_pid - first_local_elem;
      libmesh_assert_less (local_index, n_active_local_elem);

      std::vector<dof_id_type> & graph_row = _dual_graph[local_index];

      // Save this off to make it easy to index later
      _local_id_to_elem[local_index] = const_cast<Elem*>(elem);

      // Loop over the element's neighbors.  An element
      // adjacency corresponds to a face neighbor
      for (auto neighbor : elem->neighbor_ptr_range())
        {
          if (neighbor != nullptr)
            {
              // If the neighbor is active treat it
              // as a connection
              if (neighbor->active())
                {
                  libmesh_assert(_global_index_by_pid_map.count(neighbor->id()));
                  const dof_id_type neighbor_global_index_by_pid =
                    _global_index_by_pid_map[neighbor->id()];

                  graph_row.push_back(neighbor_global_index_by_pid);
                }

#ifdef LIBMESH_ENABLE_AMR

              // Otherwise we need to find all of the
              // neighbor's children that are connected to
              // us and add them
              else
                {
                  // The side of the neighbor to which
                  // we are connected
                  const unsigned int ns =
                    neighbor->which_neighbor_am_i (elem);
                  libmesh_assert_less (ns, neighbor->n_neighbors());

                  // Get all the active children (& grandchildren, etc...)
                  // of the neighbor

                  // FIXME - this is the wrong thing, since we
                  // should be getting the active family tree on
                  // our side only.  But adding too many graph
                  // links may cause hanging nodes to tend to be
                  // on partition interiors, which would reduce
                  // communication overhead for constraint
                  // equations, so we'll leave it.

                  neighbor->active_family_tree (neighbors_offspring);

                  // Get all the neighbor's children that
                  // live on that side and are thus connected
                  // to us
                  for (const auto & child : neighbors_offspring)
                    {
                      // This does not assume a level-1 mesh.
                      // Note that since children have sides numbered
                      // coincident with the parent then this is a sufficient test.
                      if (child->neighbor_ptr(ns) == elem)
                        {
                          libmesh_assert (child->active());
                          libmesh_assert (_global_index_by_pid_map.count(child->id()));
                          const dof_id_type child_global_index_by_pid =
                            _global_index_by_pid_map[child->id()];

                          graph_row.push_back(child_global_index_by_pid);
                        }
                    }
                }

#endif /* ifdef LIBMESH_ENABLE_AMR */


            }
        }

      if ((elem->dim() < LIBMESH_DIM) &&
          elem->interior_parent())
        {
          // get all relevant interior elements
          std::set<const Elem *> neighbor_set;
          elem->find_interior_neighbors(neighbor_set);

          for (const auto & neighbor : neighbor_set)
            {
              const dof_id_type neighbor_global_index_by_pid =
                _global_index_by_pid_map[neighbor->id()];

              graph_row.push_back(neighbor_global_index_by_pid);
            }
        }

      // Check for any boundary neighbors
      for (const auto & pr : as_range(interior_to_boundary_map.equal_range(elem)))
        {
          const Elem * neighbor = pr.second;

          const dof_id_type neighbor_global_index_by_pid =
            _global_index_by_pid_map[neighbor->id()];

          graph_row.push_back(neighbor_global_index_by_pid);
        }

      // Check for any constraining elements
      if (!mesh_constrained_nodes.empty()) // quick test for non-IGA cases
        {
          const auto end_it = mesh_constrained_nodes.end();

          // Use a set to avoid duplicates.  Use a well-defined method
          // of ordering that set to make debugging easier.
          std::set<const Elem *, CompareElemIdsByLevel> constraining_elems;
          for (const Node & node : elem->node_ref_range())
            {
              if (const auto row_it = mesh_constrained_nodes.find(&node);
                  row_it != end_it)
                for (const auto & [pr, coef] : row_it->second)
                  {
                    libmesh_ignore(coef); // avoid gcc 7 warning
                    constraining_elems.insert(pr.first);
                  }
            }
          for (const Elem * constraining_elem : constraining_elems)
            {
              const dof_id_type constraining_global_index_by_pid =
                _global_index_by_pid_map[constraining_elem->id()];

              graph_row.push_back(constraining_global_index_by_pid);

              // We can't be sure if the constraining element's owner sees
              // the assembly element, so to get a symmetric connectivity
              // graph we'll need to tell them about us to be safe.
              if (constraining_elem->processor_id() != mesh.processor_id())
                connections_to_push[constraining_elem->processor_id()].emplace_back
                  (global_index_by_pid, constraining_global_index_by_pid);
            }
        }

      // Check for any constrained elements
      for (const auto & pr : as_range(elems_constrained_by.equal_range(elem)))
        {
          const Elem * constrained = pr.second;
          const dof_id_type constrained_global_index_by_pid =
            _global_index_by_pid_map[constrained->id()];

          graph_row.push_back(constrained_global_index_by_pid);

          // We can't be sure if the constrained element's owner sees
          // the assembly element, so to get a symmetric connectivity
          // graph we'll need to tell them about us to be safe.
          if (constrained->processor_id() != mesh.processor_id())
            connections_to_push[constrained->processor_id()].emplace_back
              (global_index_by_pid, constrained_global_index_by_pid);
        }
    }

  // Partitioners like Parmetis require a symmetric adjacency matrix,
  // but if we have an assembly element constrained by a spline
  // NodeElem owned by another processor, it's possible that that
  // processor doesn't see our assembly element.  Let's push those
  // entries, to ensure they're counted on both sides.
  auto symmetrize_entries =
    [this, first_local_elem]
    (processor_id_type /*src_pid*/,
     const std::vector<std::pair<dof_id_type, dof_id_type>> & incoming_entries)
    {
      for (auto [i, j] : incoming_entries)
        {
          libmesh_assert_greater_equal(j, first_local_elem);
          const std::size_t jl = j - first_local_elem;
          libmesh_assert_less(jl, _dual_graph.size());
          std::vector<dof_id_type> & graph_row = _dual_graph[jl];
          if (std::find(graph_row.begin(), graph_row.end(), i) == graph_row.end())
          {
//            std::cerr << "Pushing back (" << j << ", " << i << ") from " << src_pid << std::endl;
            graph_row.push_back(i);
          }
        }
    };

  Parallel::push_parallel_vector_data(mesh.comm(),
                                      connections_to_push,
                                      symmetrize_entries);

  // *Now* we should have a symmetric adjacency matrix.  Let's check
  // that, so any failures get caught before they e.g. confuse
  // Parmetis in hard-to-debug ways.  That's a global communication so
  // we'll only do it in debug mode.
#ifdef DEBUG
  auto n_proc = mesh.n_processors();
  std::vector<dof_id_type> first_local_index_on_proc(n_proc, 0);
  for (auto pid : make_range(1u,n_proc))
    first_local_index_on_proc[pid] = first_local_index_on_proc[pid-1] + _n_active_elem_on_proc[pid-1];

  libmesh_assert_equal_to(first_local_index_on_proc[mesh.processor_id()],
                          first_local_elem);

  std::unordered_map<processor_id_type, std::vector<std::pair<dof_id_type, dof_id_type>>> entries_to_send;
  for (auto il : index_range(_dual_graph))
    {
      const std::vector<dof_id_type> & graph_row = _dual_graph[il];

      const auto i = il + first_local_elem;

      for (auto j : graph_row)
        {
          // Stupid graph rows aren't sorted yet...
          processor_id_type target_pid = 0;
          while (target_pid+1 < n_proc &&
                 j >= first_local_index_on_proc[target_pid+1])
            ++target_pid;

          entries_to_send[target_pid].emplace_back(i,j);
        }
    }

  std::vector<std::tuple<processor_id_type, dof_id_type, dof_id_type>> bad_entries;

  auto check_incoming_entries =
    [this, first_local_elem, &bad_entries]
    (processor_id_type src_pid,
     const std::vector<std::pair<dof_id_type, dof_id_type>> & incoming_entries)
    {
      for (auto [i, j] : incoming_entries)
        {
          if (j < first_local_elem)
            {
              bad_entries.emplace_back(src_pid,i,j);
              continue;
            }
          const std::size_t jl = j - first_local_elem;
          if (jl >= _dual_graph.size())
            {
              bad_entries.emplace_back(src_pid,i,j);
              continue;
            }
          const std::vector<dof_id_type> & graph_row = _dual_graph[jl];
          if (std::find(graph_row.begin(), graph_row.end(), i) ==
              graph_row.end())
            {
              bad_entries.emplace_back(src_pid,i,j);
              continue;
            }
        }
    };

  // Keep any failures in sync in parallel, for easier debugging in
  // unit tests where the failure exception will be caught.
  Parallel::push_parallel_vector_data
    (mesh.comm(), entries_to_send, check_incoming_entries);
  bool bad_entries_exist = !bad_entries.empty();
  mesh.comm().max(bad_entries_exist);
  if (bad_entries_exist)
    {
#if 0  // Optional verbosity for if this breaks again...
      if (!bad_entries.empty())
        {
          std::cerr << "Bad entries on processor " << mesh.processor_id() << ": ";
          for (auto [p, i, j] : bad_entries)
            std::cerr << '(' << p << ", " << i << ", " << j << "), ";
          std::cerr << std::endl;
        }
#endif
      libmesh_error_msg("Asymmetric partitioner graph detected");
    }
#endif
}

clone()

virtual std::unique_ptr<Partitioner> libMesh::MappedSubdomainPartitioner::clone ( ) const

inlineoverridevirtual

Returns

A copy of this partitioner wrapped in a smart pointer.

Implements libMesh::Partitioner.

Definition at line 64 of file mapped_subdomain_partitioner.h.

  {
    return std::make_unique<MappedSubdomainPartitioner>(*this);
  }

operator=() [1/2]

MappedSubdomainPartitioner& libMesh::MappedSubdomainPartitioner::operator= ( const MappedSubdomainPartitioner &  )

default

operator=() [2/2]

MappedSubdomainPartitioner& libMesh::MappedSubdomainPartitioner::operator= ( MappedSubdomainPartitioner &&  )

default

partition() [1/2]

void libMesh::Partitioner::partition ( MeshBase &  mesh, const unsigned int  n  )

virtualinherited

Partitions the MeshBase into n parts by setting processor_id() on Nodes and Elems.

Note

If you are implementing a new type of Partitioner, you most likely do not want to override the partition() function, see instead the protected virtual _do_partition() method below. The partition() function is responsible for doing a lot of libmesh-internals-specific setup and finalization before and after the _do_partition() function is called. The only responsibility of the _do_partition() function, on the other hand, is to set the processor IDs of the elements according to a specific partitioning algorithm. See, e.g. MetisPartitioner for an example.

Definition at line 196 of file partitioner.C.

References libMesh::Partitioner::_do_partition(), libMesh::ParallelObject::comm(), libMesh::MeshTools::libmesh_assert_valid_remote_elems(), mesh, libMesh::MeshBase::n_active_elem(), libMesh::Partitioner::partition_unpartitioned_elements(), libMesh::MeshBase::redistribute(), libMesh::MeshBase::set_n_partitions(), libMesh::Partitioner::set_node_processor_ids(), libMesh::Partitioner::set_parent_processor_ids(), libMesh::Partitioner::single_partition(), and libMesh::MeshBase::update_post_partitioning().

Referenced by libMesh::ParmetisPartitioner::_do_repartition(), and libMesh::Partitioner::partition().

{
  libmesh_parallel_only(mesh.comm());

  // BSK - temporary fix while redistribution is integrated 6/26/2008
  // Uncomment this to not repartition in parallel
  //   if (!mesh.is_serial())
  //     return;

  // we cannot partition into more pieces than we have
  // active elements!
  const unsigned int n_parts =
    static_cast<unsigned int>
    (std::min(mesh.n_active_elem(), static_cast<dof_id_type>(n)));

  // Set the number of partitions in the mesh
  mesh.set_n_partitions()=n_parts;

  if (n_parts == 1)
    {
      this->single_partition (mesh);
      return;
    }

  // First assign a temporary partitioning to any unpartitioned elements
  Partitioner::partition_unpartitioned_elements(mesh, n_parts);

  // Call the partitioning function
  this->_do_partition(mesh,n_parts);

  // Set the parent's processor ids
  Partitioner::set_parent_processor_ids(mesh);

  // Redistribute elements if necessary, before setting node processor
  // ids, to make sure those will be set consistently
  mesh.redistribute();

#ifdef DEBUG
  MeshTools::libmesh_assert_valid_remote_elems(mesh);

  // Messed up elem processor_id()s can leave us without the child
  // elements we need to restrict vectors on a distributed mesh
  MeshTools::libmesh_assert_valid_procids<Elem>(mesh);
#endif

  // Set the node's processor ids
  Partitioner::set_node_processor_ids(mesh);

#ifdef DEBUG
  MeshTools::libmesh_assert_valid_procids<Elem>(mesh);
#endif

  // Give derived Mesh classes a chance to update any cached data to
  // reflect the new partitioning
  mesh.update_post_partitioning();
}

partition() [2/2]

void libMesh::Partitioner::partition ( MeshBase &  mesh )

virtualinherited

Partitions the MeshBase into mesh.n_processors() by setting processor_id() on Nodes and Elems.

Note

If you are implementing a new type of Partitioner, you most likely do not want to override the partition() function, see instead the protected virtual _do_partition() method below. The partition() function is responsible for doing a lot of libmesh-internals-specific setup and finalization before and after the _do_partition() function is called. The only responsibility of the _do_partition() function, on the other hand, is to set the processor IDs of the elements according to a specific partitioning algorithm. See, e.g. MetisPartitioner for an example.

Definition at line 189 of file partitioner.C.

References mesh, libMesh::ParallelObject::n_processors(), and libMesh::Partitioner::partition().

{
  this->partition(mesh,mesh.n_processors());
}

partition_range()

void libMesh::MappedSubdomainPartitioner::partition_range ( MeshBase &  mesh, MeshBase::element_iterator  it, MeshBase::element_iterator  end, const unsigned int  n  )

overridevirtual

Called by the SubdomainPartitioner to partition elements in the range (it, end).

Reimplemented from libMesh::Partitioner.

Definition at line 38 of file mapped_subdomain_partitioner.C.

References libMesh::as_range(), libMesh::Partitioner::single_partition_range(), and subdomain_to_proc.

Referenced by _do_partition().

{
  libmesh_assert_greater (n, 0);

  // Check for an easy return.  If the user has not specified any
  // entries in subdomain_to_proc, we just do a single partitioning.
  if ((n == 1) || subdomain_to_proc.empty())
    {
      this->single_partition_range (it, end);
      return;
    }

  // Now actually do the partitioning.
  LOG_SCOPE ("partition_range()", "MappedSubdomainPartitioner");

  for (auto & elem : as_range(it, end))
    {
      subdomain_id_type sbd_id = elem->subdomain_id();

      // Find which processor id corresponds to this element's subdomain id.
      elem->processor_id() = libmesh_map_find(subdomain_to_proc, sbd_id);
    }
}

partition_unpartitioned_elements() [1/2]

void libMesh::Partitioner::partition_unpartitioned_elements ( MeshBase &  mesh )

staticinherited

These functions assign processor IDs to newly-created elements (in parallel) which are currently assigned to processor 0.

Definition at line 345 of file partitioner.C.

References mesh, and libMesh::ParallelObject::n_processors().

Referenced by libMesh::Partitioner::partition(), and libMesh::Partitioner::repartition().

{
  Partitioner::partition_unpartitioned_elements(mesh, mesh.n_processors());
}

partition_unpartitioned_elements() [2/2]

void libMesh::Partitioner::partition_unpartitioned_elements ( MeshBase &  mesh, const unsigned int  n  )

staticinherited

Definition at line 352 of file partitioner.C.

References libMesh::as_range(), libMesh::ParallelObject::comm(), libMesh::MeshTools::create_bounding_box(), distance(), libMesh::MeshCommunication::find_global_indices(), libMesh::make_range(), mesh, libMesh::MeshTools::n_elem(), and libMesh::ParallelObject::n_processors().

{
  MeshBase::element_iterator       it  = mesh.unpartitioned_elements_begin();
  const MeshBase::element_iterator end = mesh.unpartitioned_elements_end();

  const dof_id_type n_unpartitioned_elements = MeshTools::n_elem (it, end);

  // the unpartitioned elements must exist on all processors. If the range is empty on one
  // it is empty on all, and we can quit right here.
  if (!n_unpartitioned_elements)
    return;

  // find the target subdomain sizes
  std::vector<dof_id_type> subdomain_bounds(mesh.n_processors());

  for (auto pid : make_range(mesh.n_processors()))
    {
      dof_id_type tgt_subdomain_size = 0;

      // watch out for the case that n_subdomains < n_processors
      if (pid < n_subdomains)
        {
          tgt_subdomain_size = n_unpartitioned_elements/n_subdomains;

          if (pid < n_unpartitioned_elements%n_subdomains)
            tgt_subdomain_size++;

        }

      //libMesh::out << "pid, #= " << pid << ", " << tgt_subdomain_size << std::endl;
      if (pid == 0)
        subdomain_bounds[0] = tgt_subdomain_size;
      else
        subdomain_bounds[pid] = subdomain_bounds[pid-1] + tgt_subdomain_size;
    }

  libmesh_assert_equal_to (subdomain_bounds.back(), n_unpartitioned_elements);

  // create the unique mapping for all unpartitioned elements independent of partitioning
  // determine the global indexing for all the unpartitioned elements
  std::vector<dof_id_type> global_indices;

  // Calling this on all processors a unique range in [0,n_unpartitioned_elements) is constructed.
  // Only the indices for the elements we pass in are returned in the array.
  MeshCommunication().find_global_indices (mesh.comm(),
                                           MeshTools::create_bounding_box(mesh), it, end,
                                           global_indices);

  dof_id_type cnt=0;
  for (auto & elem : as_range(it, end))
    {
      libmesh_assert_less (cnt, global_indices.size());
      const dof_id_type global_index =
        global_indices[cnt++];

      libmesh_assert_less (global_index, subdomain_bounds.back());
      libmesh_assert_less (global_index, n_unpartitioned_elements);

      const processor_id_type subdomain_id =
        cast_int<processor_id_type>
        (std::distance(subdomain_bounds.begin(),
                       std::upper_bound(subdomain_bounds.begin(),
                                        subdomain_bounds.end(),
                                        global_index)));
      libmesh_assert_less (subdomain_id, n_subdomains);

      elem->processor_id() = subdomain_id;
      //libMesh::out << "assigning " << global_index << " to " << subdomain_id << std::endl;
    }
}

processor_pairs_to_interface_nodes()

void libMesh::Partitioner::processor_pairs_to_interface_nodes ( MeshBase &  mesh, std::map< std::pair< processor_id_type, processor_id_type >, std::set< dof_id_type >> &  processor_pair_to_nodes  )

staticinherited

On the partitioning interface, a surface is shared by two and only two processors.

Try to find which pair of processors corresponds to which surfaces, and store their nodes.

Definition at line 579 of file partitioner.C.

References libMesh::ParallelObject::comm(), libMesh::DofObject::invalid_processor_id, libMesh::libmesh_assert(), mesh, and n_nodes.

Referenced by libMesh::Partitioner::set_interface_node_processor_ids_BFS(), libMesh::Partitioner::set_interface_node_processor_ids_linear(), and libMesh::Partitioner::set_interface_node_processor_ids_petscpartitioner().

{
  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

  processor_pair_to_nodes.clear();

  std::set<dof_id_type> mynodes;
  std::set<dof_id_type> neighbor_nodes;
  std::vector<dof_id_type> common_nodes;

  // Loop over all the active elements
  for (auto & elem : mesh.active_element_ptr_range())
    {
      libmesh_assert(elem);

      libmesh_assert_not_equal_to (elem->processor_id(), DofObject::invalid_processor_id);

      auto n_nodes = elem->n_nodes();

      // prepare data for this element
      mynodes.clear();
      neighbor_nodes.clear();
      common_nodes.clear();

      for (unsigned int inode = 0; inode < n_nodes; inode++)
        mynodes.insert(elem->node_id(inode));

      for (auto i : elem->side_index_range())
        {
          auto neigh = elem->neighbor_ptr(i);
          if (neigh && !neigh->is_remote() && neigh->processor_id() != elem->processor_id())
            {
              neighbor_nodes.clear();
              common_nodes.clear();
              auto neigh_n_nodes = neigh->n_nodes();
              for (unsigned int inode = 0; inode < neigh_n_nodes; inode++)
                neighbor_nodes.insert(neigh->node_id(inode));

              std::set_intersection(mynodes.begin(), mynodes.end(),
                                    neighbor_nodes.begin(), neighbor_nodes.end(),
                                    std::back_inserter(common_nodes));

              auto & map_set = processor_pair_to_nodes[std::make_pair(std::min(elem->processor_id(), neigh->processor_id()),
                                                                      std::max(elem->processor_id(), neigh->processor_id()))];
              for (auto global_node_id : common_nodes)
                map_set.insert(global_node_id);
            }
        }
    }
}

repartition() [1/2]

void libMesh::Partitioner::repartition ( MeshBase &  mesh, const unsigned int  n  )

inherited

Repartitions the MeshBase into n parts.

(Some partitioning algorithms can repartition more efficiently than computing a new partitioning from scratch.) The default behavior is to simply call this->partition(mesh,n).

Definition at line 263 of file partitioner.C.

References libMesh::Partitioner::_do_repartition(), mesh, libMesh::MeshBase::n_active_elem(), libMesh::Partitioner::partition_unpartitioned_elements(), libMesh::MeshBase::set_n_partitions(), libMesh::Partitioner::set_node_processor_ids(), libMesh::Partitioner::set_parent_processor_ids(), and libMesh::Partitioner::single_partition().

Referenced by libMesh::Partitioner::repartition().

{
  // we cannot partition into more pieces than we have
  // active elements!
  const unsigned int n_parts =
    static_cast<unsigned int>
    (std::min(mesh.n_active_elem(), static_cast<dof_id_type>(n)));

  // Set the number of partitions in the mesh
  mesh.set_n_partitions()=n_parts;

  if (n_parts == 1)
    {
      this->single_partition (mesh);
      return;
    }

  // First assign a temporary partitioning to any unpartitioned elements
  Partitioner::partition_unpartitioned_elements(mesh, n_parts);

  // Call the partitioning function
  this->_do_repartition(mesh,n_parts);

  // Set the parent's processor ids
  Partitioner::set_parent_processor_ids(mesh);

  // Set the node's processor ids
  Partitioner::set_node_processor_ids(mesh);
}

repartition() [2/2]

void libMesh::Partitioner::repartition ( MeshBase &  mesh )

inherited

Repartitions the MeshBase into mesh.n_processors() parts.

This is required since some partitioning algorithms can repartition more efficiently than computing a new partitioning from scratch.

Definition at line 256 of file partitioner.C.

References mesh, libMesh::ParallelObject::n_processors(), and libMesh::Partitioner::repartition().

{
  this->repartition(mesh,mesh.n_processors());
}

set_interface_node_processor_ids_BFS()

void libMesh::Partitioner::set_interface_node_processor_ids_BFS ( MeshBase &  mesh )

staticinherited

Nodes on the partitioning interface is clustered into two groups BFS (Breadth First Search)scheme for per pair of processors.

Definition at line 657 of file partitioner.C.

References libMesh::MeshTools::build_nodes_to_elem_map(), libMesh::ParallelObject::comm(), libMesh::MeshTools::find_nodal_neighbors(), mesh, libMesh::MeshBase::node_ref(), libMesh::DofObject::processor_id(), and libMesh::Partitioner::processor_pairs_to_interface_nodes().

Referenced by libMesh::Partitioner::set_node_processor_ids().

{
  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

  // I see occasional consistency failures when using this on a
  // distributed mesh
  libmesh_experimental();

  std::map<std::pair<processor_id_type, processor_id_type>, std::set<dof_id_type>> processor_pair_to_nodes;

  processor_pairs_to_interface_nodes(mesh, processor_pair_to_nodes);

  std::unordered_map<dof_id_type, std::vector<const Elem *>> nodes_to_elem_map;

  MeshTools::build_nodes_to_elem_map(mesh, nodes_to_elem_map);

  std::vector<const Node *>  neighbors;
  std::set<dof_id_type> neighbors_order;
  std::vector<dof_id_type> common_nodes;
  std::queue<dof_id_type> nodes_queue;
  std::set<dof_id_type> visted_nodes;

  for (auto & pmap : processor_pair_to_nodes)
    {
      std::size_t n_own_nodes = pmap.second.size()/2;

      // Initialize node assignment
      for (dof_id_type id : pmap.second)
        mesh.node_ref(id).processor_id() = pmap.first.second;

      visted_nodes.clear();
      for (dof_id_type id : pmap.second)
        {
          mesh.node_ref(id).processor_id() = pmap.first.second;

          if (visted_nodes.count(id))
            continue;
          else
            {
              nodes_queue.push(id);
              visted_nodes.insert(id);
              if (visted_nodes.size() >= n_own_nodes)
                break;
            }

          while (!nodes_queue.empty())
            {
              auto & node = mesh.node_ref(nodes_queue.front());
              nodes_queue.pop();

              neighbors.clear();
              MeshTools::find_nodal_neighbors(mesh, node, nodes_to_elem_map, neighbors);
              neighbors_order.clear();
              for (auto & neighbor : neighbors)
                neighbors_order.insert(neighbor->id());

              common_nodes.clear();
              std::set_intersection(pmap.second.begin(), pmap.second.end(),
                                    neighbors_order.begin(), neighbors_order.end(),
                                    std::back_inserter(common_nodes));

              for (auto c_node : common_nodes)
                if (!visted_nodes.count(c_node))
                  {
                    nodes_queue.push(c_node);
                    visted_nodes.insert(c_node);
                    if (visted_nodes.size() >= n_own_nodes)
                      goto queue_done;
                  }

              if (visted_nodes.size() >= n_own_nodes)
                goto queue_done;
            }
        }
    queue_done:
      for (auto node : visted_nodes)
        mesh.node_ref(node).processor_id() = pmap.first.first;
    }
}

set_interface_node_processor_ids_linear()

void libMesh::Partitioner::set_interface_node_processor_ids_linear ( MeshBase &  mesh )

staticinherited

Nodes on the partitioning interface is linearly assigned to each pair of processors.

Definition at line 632 of file partitioner.C.

References libMesh::ParallelObject::comm(), mesh, libMesh::MeshBase::node_ref(), libMesh::DofObject::processor_id(), and libMesh::Partitioner::processor_pairs_to_interface_nodes().

Referenced by libMesh::Partitioner::set_node_processor_ids().

{
  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

  std::map<std::pair<processor_id_type, processor_id_type>, std::set<dof_id_type>> processor_pair_to_nodes;

  processor_pairs_to_interface_nodes(mesh, processor_pair_to_nodes);

  for (auto & pmap : processor_pair_to_nodes)
    {
      std::size_t n_own_nodes = pmap.second.size()/2, i = 0;

      for (dof_id_type id : pmap.second)
        {
          auto & node = mesh.node_ref(id);
          if (i <= n_own_nodes)
            node.processor_id() = pmap.first.first;
          else
            node.processor_id() = pmap.first.second;
          i++;
        }
    }
}

set_interface_node_processor_ids_petscpartitioner()

void libMesh::Partitioner::set_interface_node_processor_ids_petscpartitioner ( MeshBase &  mesh )

staticinherited

Nodes on the partitioning interface is partitioned into two groups using a PETSc partitioner for each pair of processors.

Definition at line 738 of file partitioner.C.

References libMesh::MeshTools::build_nodes_to_elem_map(), libMesh::ParallelObject::comm(), libMesh::MeshTools::find_nodal_neighbors(), libMesh::WrappedPetsc< T >::get(), libMesh::is, libMesh::libmesh_ignore(), mesh, libMesh::MeshBase::node_ref(), libMesh::DofObject::processor_id(), and libMesh::Partitioner::processor_pairs_to_interface_nodes().

Referenced by libMesh::Partitioner::set_node_processor_ids().

{
  libmesh_ignore(mesh); // Only used if LIBMESH_HAVE_PETSC

  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

#if LIBMESH_HAVE_PETSC
  std::map<std::pair<processor_id_type, processor_id_type>, std::set<dof_id_type>> processor_pair_to_nodes;

  processor_pairs_to_interface_nodes(mesh, processor_pair_to_nodes);

  std::vector<std::vector<const Elem *>> nodes_to_elem_map;

  MeshTools::build_nodes_to_elem_map(mesh, nodes_to_elem_map);

  std::vector<const Node *>  neighbors;
  std::set<dof_id_type> neighbors_order;
  std::vector<dof_id_type> common_nodes;

  std::vector<dof_id_type> rows;
  std::vector<dof_id_type> cols;

  std::map<dof_id_type, dof_id_type> global_to_local;

  for (auto & pmap : processor_pair_to_nodes)
    {
      unsigned int i = 0;

      rows.clear();
      rows.resize(pmap.second.size()+1);
      cols.clear();
      for (dof_id_type id : pmap.second)
        global_to_local[id] = i++;

      i = 0;
      for (auto id : pmap.second)
        {
          auto & node = mesh.node_ref(id);
          neighbors.clear();
          MeshTools::find_nodal_neighbors(mesh, node, nodes_to_elem_map, neighbors);
          neighbors_order.clear();
          for (auto & neighbor : neighbors)
            neighbors_order.insert(neighbor->id());

          common_nodes.clear();
          std::set_intersection(pmap.second.begin(), pmap.second.end(),
                                neighbors_order.begin(), neighbors_order.end(),
                                std::back_inserter(common_nodes));

          rows[i+1] = rows[i] + cast_int<dof_id_type>(common_nodes.size());

          for (auto c_node : common_nodes)
            cols.push_back(global_to_local[c_node]);

          i++;
        }

      // Next we construct an IS from a MatPartitioning
      WrappedPetsc<IS> is;
      {
        PetscInt *adj_i, *adj_j;
        LibmeshPetscCall2(mesh.comm(), PetscCalloc1(rows.size(), &adj_i));
        LibmeshPetscCall2(mesh.comm(), PetscCalloc1(cols.size(), &adj_j));
        PetscInt rows_size = cast_int<PetscInt>(rows.size());
        for (PetscInt ii=0; ii<rows_size; ii++)
          adj_i[ii] = rows[ii];

        PetscInt cols_size = cast_int<PetscInt>(cols.size());
        for (PetscInt ii=0; ii<cols_size; ii++)
          adj_j[ii] = cols[ii];

        const PetscInt sz = cast_int<PetscInt>(pmap.second.size());

        // Create sparse matrix representing an adjacency list
        WrappedPetsc<Mat> adj;
        LibmeshPetscCall2(mesh.comm(), MatCreateMPIAdj(PETSC_COMM_SELF, sz, sz, adj_i, adj_j, nullptr, adj.get()));

        // Create MatPartitioning object
        WrappedPetsc<MatPartitioning> part;
        LibmeshPetscCall2(mesh.comm(), MatPartitioningCreate(PETSC_COMM_SELF, part.get()));

        // Apply MatPartitioning, storing results in "is"
        LibmeshPetscCall2(mesh.comm(), MatPartitioningSetAdjacency(part, adj));
        LibmeshPetscCall2(mesh.comm(), MatPartitioningSetNParts(part, 2));
        LibmeshPetscCall2(mesh.comm(), PetscObjectSetOptionsPrefix((PetscObject)(*part), "balance_"));
        LibmeshPetscCall2(mesh.comm(), MatPartitioningSetFromOptions(part));
        LibmeshPetscCall2(mesh.comm(), MatPartitioningApply(part, is.get()));
      }

      PetscInt local_size;
      const PetscInt *indices;
      LibmeshPetscCall2(mesh.comm(), ISGetLocalSize(is, &local_size));
      LibmeshPetscCall2(mesh.comm(), ISGetIndices(is, &indices));

      i = 0;
      for (auto id : pmap.second)
        {
          auto & node = mesh.node_ref(id);
          if (indices[i])
            node.processor_id() = pmap.first.second;
          else
            node.processor_id() = pmap.first.first;

          i++;
        }
      LibmeshPetscCall2(mesh.comm(), ISRestoreIndices(is, &indices));
    }
#else
  libmesh_error_msg("PETSc is required");
#endif
}

set_node_processor_ids()

void libMesh::Partitioner::set_node_processor_ids ( MeshBase &  mesh )

staticinherited

This function is called after partitioning to set the processor IDs for the nodes.

By definition, a Node's processor ID is the minimum processor ID for all of the elements which share the node.

Definition at line 852 of file partitioner.C.

References libMesh::as_range(), libMesh::Node::choose_processor_id(), libMesh::ParallelObject::comm(), libMesh::DofObject::id(), libMesh::DofObject::invalid_processor_id, libMesh::MeshBase::is_serial(), libMesh::libmesh_assert(), mesh, libMesh::MeshTools::n_elem(), libMesh::MeshTools::n_levels(), libMesh::MeshBase::node_ref(), libMesh::on_command_line(), libMesh::DofObject::processor_id(), libMesh::Partitioner::set_interface_node_processor_ids_BFS(), libMesh::Partitioner::set_interface_node_processor_ids_linear(), libMesh::Partitioner::set_interface_node_processor_ids_petscpartitioner(), and libMesh::Parallel::sync_node_data_by_element_id().

Referenced by libMesh::MeshRefinement::_refine_elements(), libMesh::UnstructuredMesh::all_first_order(), libMesh::Partitioner::partition(), libMesh::XdrIO::read(), libMesh::Partitioner::repartition(), and libMesh::BoundaryInfo::sync().

{
  LOG_SCOPE("set_node_processor_ids()","Partitioner");

  // This function must be run on all processors at once
  libmesh_parallel_only(mesh.comm());

  // If we have any unpartitioned elements at this
  // stage there is a problem
  libmesh_assert (MeshTools::n_elem(mesh.unpartitioned_elements_begin(),
                                    mesh.unpartitioned_elements_end()) == 0);

  // Start from scratch here: nodes we used to own may not be
  // eligible for us to own any more.
  for (auto & node : mesh.node_ptr_range())
    {
      node->processor_id() = DofObject::invalid_processor_id;
    }

  // Loop over all the active elements
  for (auto & elem : mesh.active_element_ptr_range())
    {
      libmesh_assert(elem);

      libmesh_assert_not_equal_to (elem->processor_id(), DofObject::invalid_processor_id);

      // Consider updating the processor id on this element's nodes
      for (Node & node : elem->node_ref_range())
        {
          processor_id_type & pid = node.processor_id();
          pid = node.choose_processor_id(pid, elem->processor_id());
        }
    }

  // How we finish off the node partitioning depends on our command
  // line options.

  const bool load_balanced_nodes_linear =
      libMesh::on_command_line ("--load-balanced-nodes-linear");

  const bool load_balanced_nodes_bfs =
       libMesh::on_command_line ("--load-balanced-nodes-bfs");

  const bool load_balanced_nodes_petscpartition =
      libMesh::on_command_line ("--load-balanced-nodes-petscpartitioner");

  unsigned int n_load_balance_options = load_balanced_nodes_linear;
  n_load_balance_options += load_balanced_nodes_bfs;
  n_load_balance_options += load_balanced_nodes_petscpartition;
  libmesh_error_msg_if(n_load_balance_options > 1,
                       "Cannot perform more than one load balancing type at a time");

  if (load_balanced_nodes_linear)
    set_interface_node_processor_ids_linear(mesh);
  else if (load_balanced_nodes_bfs)
    set_interface_node_processor_ids_BFS(mesh);
  else if (load_balanced_nodes_petscpartition)
    set_interface_node_processor_ids_petscpartitioner(mesh);

   // Node balancing algorithm will response to assign owned nodes.
   // We still need to sync PIDs
  {
    // For inactive elements, we will have already gotten most of
    // these nodes, *except* for the case of a parent with a subset
    // of active descendants which are remote elements.  In that
    // case some of the parent nodes will not have been properly
    // handled yet on our processor.
    //
    // We don't want to inadvertently give one of them an incorrect
    // processor id, but if we're not in serial then we have to
    // assign them temporary pids to make querying work, so we'll
    // save our *valid* pids before assigning temporaries.
    //
    // Even in serial we'll want to check and make sure we're not
    // overwriting valid active node pids with pids from subactive
    // elements.
    std::unordered_set<dof_id_type> bad_pids;

    for (auto & node : mesh.node_ptr_range())
      if (node->processor_id() == DofObject::invalid_processor_id)
        bad_pids.insert(node->id());

    // If we assign our temporary ids by looping from finer elements
    // to coarser elements, we'll always get an id from the finest
    // ghost element we can see, which will usually be "closer" to
    // the true processor we want to query and so will reduce query
    // cycles that don't reach that processor.

    // But we can still end up with a query cycle that dead-ends, so
    // we need to prepare a "push" communication step here.

    const bool is_serial = mesh.is_serial();
    std::unordered_map
      <processor_id_type,
       std::unordered_map<dof_id_type, processor_id_type>>
      potential_pids;

    const unsigned int n_levels = MeshTools::n_levels(mesh);
    for (unsigned int level = n_levels; level > 0; --level)
      {
        for (auto & elem : as_range(mesh.level_elements_begin(level-1),
                                    mesh.level_elements_end(level-1)))
          {
            libmesh_assert_not_equal_to (elem->processor_id(),
                                         DofObject::invalid_processor_id);

            const processor_id_type elem_pid = elem->processor_id();

            // Consider updating the processor id on this element's nodes
            for (Node & node : elem->node_ref_range())
              {
                processor_id_type & pid = node.processor_id();
                if (bad_pids.count(node.id()))
                  pid = node.choose_processor_id(pid, elem_pid);
                else if (!is_serial)
                  potential_pids[elem_pid][node.id()] = pid;
              }
          }
      }

    if (!is_serial)
      {
        std::unordered_map
          <processor_id_type,
           std::vector<std::pair<dof_id_type, processor_id_type>>>
          potential_pids_vecs;

        for (auto & pair : potential_pids)
          potential_pids_vecs[pair.first].assign(pair.second.begin(), pair.second.end());

        auto pids_action_functor =
          [& mesh, & bad_pids]
          (processor_id_type /* src_pid */,
           const std::vector<std::pair<dof_id_type, processor_id_type>> & data)
          {
            for (auto pair : data)
              {
                Node & node = mesh.node_ref(pair.first);
                processor_id_type & pid = node.processor_id();
                if (const auto it = bad_pids.find(pair.first);
                    it != bad_pids.end())
                  {
                    pid = pair.second;
                    bad_pids.erase(it);
                  }
                else
                  pid = node.choose_processor_id(pid, pair.second);
              }
          };

        Parallel::push_parallel_vector_data
          (mesh.comm(), potential_pids_vecs, pids_action_functor);

        // Using default libMesh options, we'll just need to sync
        // between processors now.  The catch here is that we can't
        // initially trust Node::choose_processor_id() because some
        // of those node processor ids are the temporary ones.
        CorrectProcIds correct_pids(mesh, bad_pids);
        Parallel::sync_node_data_by_element_id
          (mesh, mesh.elements_begin(), mesh.elements_end(),
           Parallel::SyncEverything(), Parallel::SyncEverything(),
           correct_pids);

        // But once we've got all the non-temporary pids synced, we
        // may need to sync again to get any pids on nodes only
        // connected to subactive elements, for which *only*
        // "temporary" pids are possible.
        bad_pids.clear();
        Parallel::sync_node_data_by_element_id
          (mesh,
           mesh.elements_begin(), mesh.elements_end(),
           Parallel::SyncEverything(), Parallel::SyncEverything(),
           correct_pids);
      }
  }

  // We can't assert that all nodes are connected to elements, because
  // a DistributedMesh with NodeConstraints might have pulled in some
  // remote nodes solely for evaluating those constraints.
  // MeshTools::libmesh_assert_connected_nodes(mesh);

#ifdef DEBUG
  MeshTools::libmesh_assert_valid_procids<Node>(mesh);
  //MeshTools::libmesh_assert_canonical_node_procids(mesh);
#endif
}

set_parent_processor_ids()

void libMesh::Partitioner::set_parent_processor_ids ( MeshBase &  mesh )

staticinherited

This function is called after partitioning to set the processor IDs for the inactive parent elements.

A parent's processor ID is the same as its first child.

Definition at line 426 of file partitioner.C.

References libMesh::as_range(), libMesh::Elem::child_ref_range(), libMesh::ParallelObject::comm(), libMesh::Partitioner::communication_blocksize, libMesh::DofObject::invalid_processor_id, libMesh::DofObject::invalidate_processor_id(), libMesh::MeshBase::is_serial(), libMesh::libmesh_assert(), libMesh::libmesh_ignore(), libMesh::MeshBase::max_elem_id(), mesh, TIMPI::Communicator::min(), libMesh::MeshTools::n_elem(), libMesh::Elem::parent(), libMesh::DofObject::processor_id(), and libMesh::Elem::total_family_tree().

Referenced by libMesh::Partitioner::partition(), and libMesh::Partitioner::repartition().

{
  // Ignore the parameter when !LIBMESH_ENABLE_AMR
  libmesh_ignore(mesh);

  LOG_SCOPE("set_parent_processor_ids()", "Partitioner");

#ifdef LIBMESH_ENABLE_AMR

  // If the mesh is serial we have access to all the elements,
  // in particular all the active ones.  We can therefore set
  // the parent processor ids indirectly through their children, and
  // set the subactive processor ids while examining their active
  // ancestors.
  // By convention a parent is assigned to the minimum processor
  // of all its children, and a subactive is assigned to the processor
  // of its active ancestor.
  if (mesh.is_serial())
    {
      for (auto & elem : mesh.active_element_ptr_range())
        {
          // First set descendents
          std::vector<Elem *> subactive_family;
          elem->total_family_tree(subactive_family);
          for (const auto & f : subactive_family)
            f->processor_id() = elem->processor_id();

          // Then set ancestors
          Elem * parent = elem->parent();

          while (parent)
            {
              // invalidate the parent id, otherwise the min below
              // will not work if the current parent id is less
              // than all the children!
              parent->invalidate_processor_id();

              for (auto & child : parent->child_ref_range())
                {
                  libmesh_assert(!child.is_remote());
                  libmesh_assert_not_equal_to (child.processor_id(), DofObject::invalid_processor_id);
                  parent->processor_id() = std::min(parent->processor_id(),
                                                    child.processor_id());
                }
              parent = parent->parent();
            }
        }
    }

  // When the mesh is parallel we cannot guarantee that parents have access to
  // all their children.
  else
    {
      // Setting subactive processor ids is easy: we can guarantee
      // that children have access to all their parents.

      // Loop over all the active elements in the mesh
      for (auto & child : mesh.active_element_ptr_range())
        {
          std::vector<Elem *> subactive_family;
          child->total_family_tree(subactive_family);
          for (const auto & f : subactive_family)
            f->processor_id() = child->processor_id();
        }

      // When the mesh is parallel we cannot guarantee that parents have access to
      // all their children.

      // We will use a brute-force approach here.  Each processor finds its parent
      // elements and sets the parent pid to the minimum of its
      // semilocal descendants.
      // A global reduction is then performed to make sure the true minimum is found.
      // As noted, this is required because we cannot guarantee that a parent has
      // access to all its children on any single processor.
      libmesh_parallel_only(mesh.comm());
      libmesh_assert(MeshTools::n_elem(mesh.unpartitioned_elements_begin(),
                                       mesh.unpartitioned_elements_end()) == 0);

      const dof_id_type max_elem_id = mesh.max_elem_id();

      std::vector<processor_id_type>
        parent_processor_ids (std::min(communication_blocksize,
                                       max_elem_id));

      for (dof_id_type blk=0, last_elem_id=0; last_elem_id<max_elem_id; blk++)
        {
          last_elem_id =
            std::min(static_cast<dof_id_type>((blk+1)*communication_blocksize),
                     max_elem_id);
          const dof_id_type first_elem_id = blk*communication_blocksize;

          std::fill (parent_processor_ids.begin(),
                     parent_processor_ids.end(),
                     DofObject::invalid_processor_id);

          // first build up local contributions to parent_processor_ids
          bool have_parent_in_block = false;

          for (auto & parent : as_range(mesh.ancestor_elements_begin(),
                                        mesh.ancestor_elements_end()))
            {
              const dof_id_type parent_idx = parent->id();
              libmesh_assert_less (parent_idx, max_elem_id);

              if ((parent_idx >= first_elem_id) &&
                  (parent_idx <  last_elem_id))
                {
                  have_parent_in_block = true;
                  processor_id_type parent_pid = DofObject::invalid_processor_id;

                  std::vector<const Elem *> active_family;
                  parent->active_family_tree(active_family);
                  for (const auto & f : active_family)
                    parent_pid = std::min (parent_pid, f->processor_id());

                  const dof_id_type packed_idx = parent_idx - first_elem_id;
                  libmesh_assert_less (packed_idx, parent_processor_ids.size());

                  parent_processor_ids[packed_idx] = parent_pid;
                }
            }

          // then find the global minimum
          mesh.comm().min (parent_processor_ids);

          // and assign the ids, if we have a parent in this block.
          if (have_parent_in_block)
            for (auto & parent : as_range(mesh.ancestor_elements_begin(),
                                          mesh.ancestor_elements_end()))
              {
                const dof_id_type parent_idx = parent->id();

                if ((parent_idx >= first_elem_id) &&
                    (parent_idx <  last_elem_id))
                  {
                    const dof_id_type packed_idx = parent_idx - first_elem_id;
                    libmesh_assert_less (packed_idx, parent_processor_ids.size());

                    const processor_id_type parent_pid =
                      parent_processor_ids[packed_idx];

                    libmesh_assert_not_equal_to (parent_pid, DofObject::invalid_processor_id);

                    parent->processor_id() = parent_pid;
                  }
              }
        }
    }

#endif // LIBMESH_ENABLE_AMR
}

single_partition()

bool libMesh::Partitioner::single_partition ( MeshBase &  mesh )

protectedinherited

Trivially "partitions" the mesh for one processor.

Simply loops through the elements and assigns all of them to processor 0. Is is provided as a separate function so that derived classes may use it without reimplementing it.

Returns true iff any processor id was changed.

Definition at line 298 of file partitioner.C.

References libMesh::ParallelObject::comm(), TIMPI::Communicator::max(), mesh, libMesh::MeshBase::redistribute(), and libMesh::Partitioner::single_partition_range().

Referenced by libMesh::SubdomainPartitioner::_do_partition(), libMesh::Partitioner::partition(), and libMesh::Partitioner::repartition().

{
  bool changed_pid =
    this->single_partition_range(mesh.elements_begin(),
                                 mesh.elements_end());

  // If we have a distributed mesh with an empty rank (or where rank
  // 0 has only its own component of a disconnected mesh, I guess),
  // that rank might need to be informed of a change.
  mesh.comm().max(changed_pid);

  // We may need to redistribute, in case someone (like our unit
  // tests) is doing something silly (like moving a whole
  // already-distributed mesh back onto rank 0).
  if (changed_pid)
    mesh.redistribute();

  return changed_pid;
}

single_partition_range()

bool libMesh::Partitioner::single_partition_range ( MeshBase::element_iterator  it, MeshBase::element_iterator  end  )

protectedinherited

Slightly generalized version of single_partition which acts on a range of elements defined by the pair of iterators (it, end).

Returns true iff any processor id was changed.

Definition at line 320 of file partitioner.C.

References libMesh::as_range(), and libMesh::DofObject::processor_id().

Referenced by libMesh::LinearPartitioner::partition_range(), libMesh::MetisPartitioner::partition_range(), libMesh::SFCPartitioner::partition_range(), partition_range(), libMesh::CentroidPartitioner::partition_range(), and libMesh::Partitioner::single_partition().

{
  LOG_SCOPE("single_partition_range()", "Partitioner");

  bool changed_pid = false;

  for (auto & elem : as_range(it, end))
    {
      if (elem->processor_id())
        changed_pid = true;
      elem->processor_id() = 0;

      // Assign all this element's nodes to processor 0 as well.
      for (Node & node : elem->node_ref_range())
        {
          if (node.processor_id())
            changed_pid = true;
          node.processor_id() = 0;
        }
    }

  return changed_pid;
}

type()

PartitionerType libMesh::MappedSubdomainPartitioner::type ( ) const

overridevirtual

Reimplemented from libMesh::Partitioner.

Definition at line 32 of file mapped_subdomain_partitioner.C.

References libMesh::MAPPED_SUBDOMAIN_PARTITIONER.

{
  return MAPPED_SUBDOMAIN_PARTITIONER;
}

Member Data Documentation

_dual_graph

std::vector<std::vector<dof_id_type> > libMesh::Partitioner::_dual_graph

protectedinherited

A dual graph corresponds to the mesh, and it is typically used in paritioner.

A vertex represents an element, and its neighbors are the element neighbors.

Definition at line 302 of file partitioner.h.

Referenced by libMesh::Partitioner::build_graph().

_global_index_by_pid_map

std::unordered_map<dof_id_type, dof_id_type> libMesh::Partitioner::_global_index_by_pid_map

protectedinherited

Maps active element ids into a contiguous range, as needed by parallel partitioner.

Definition at line 286 of file partitioner.h.

Referenced by libMesh::Partitioner::_find_global_index_by_pid_map(), libMesh::Partitioner::assign_partitioning(), and libMesh::Partitioner::build_graph().

_local_id_to_elem

std::vector<Elem *> libMesh::Partitioner::_local_id_to_elem

protectedinherited

Definition at line 305 of file partitioner.h.

Referenced by libMesh::Partitioner::build_graph().

_n_active_elem_on_proc

std::vector<dof_id_type> libMesh::Partitioner::_n_active_elem_on_proc

protectedinherited

The number of active elements on each processor.

Note

ParMETIS requires that each processor have some active elements; it will abort if any processor passes a nullptr _part array.

Definition at line 295 of file partitioner.h.

Referenced by libMesh::Partitioner::_find_global_index_by_pid_map(), libMesh::Partitioner::assign_partitioning(), and libMesh::Partitioner::build_graph().

_weights

ErrorVector* libMesh::Partitioner::_weights

protectedinherited

The weights that might be used for partitioning.

Definition at line 281 of file partitioner.h.

Referenced by libMesh::MetisPartitioner::attach_weights(), and libMesh::MetisPartitioner::partition_range().

communication_blocksize

const dof_id_type libMesh::Partitioner::communication_blocksize

staticprotectedinherited

Initial value:

=
  dof_id_type(1000000)

The blocksize to use when doing blocked parallel communication.

This limits the maximum vector size which can be used in a single communication step.

Definition at line 258 of file partitioner.h.

Referenced by libMesh::Partitioner::set_parent_processor_ids().

subdomain_to_proc

std::map<subdomain_id_type, processor_id_type> libMesh::MappedSubdomainPartitioner::subdomain_to_proc

Before calling partition() or partition_range(), the user must assign all the Mesh subdomains to certain processors by adding them to this std::map.

For example: subdomain_to_proc[1] = 0; subdomain_to_proc[2] = 0; subdomain_to_proc[3] = 0; subdomain_to_proc[4] = 1; subdomain_to_proc[5] = 1; subdomain_to_proc[6] = 2; Would partition the mesh onto three processors, with subdomains 1, 2, and 3 on processor 0, subdomains 4 and 5 on processor 1, and subdomain 6 on processor 2.

Definition at line 83 of file mapped_subdomain_partitioner.h.

Referenced by partition_range().

---

The documentation for this class was generated from the following files:

• include/partitioning/mapped_subdomain_partitioner.h
• src/partitioning/mapped_subdomain_partitioner.C