void Partitioner::set_node_processor_ids(MeshBase & mesh)
{
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);
// const dof_id_type orig_n_local_nodes = mesh.n_local_nodes();
// libMesh::err << "[" << mesh.processor_id() << "]: orig_n_local_nodes="
// << orig_n_local_nodes << std::endl;
// Build up request sets. Each node is currently owned by a processor because
// it is connected to an element owned by that processor. However, during the
// repartitioning phase that element may have been assigned a new processor id, but
// it is still resident on the original processor. We need to know where to look
// for new ids before assigning new ids, otherwise we may be asking the wrong processors
// for the wrong information.
//
// The only remaining issue is what to do with unpartitioned nodes. Since they are required
// to live on all processors we can simply rely on ourselves to number them properly.
std::vector<std::vector<dof_id_type>>
requested_node_ids(mesh.n_processors());
// Loop over all the nodes, count the ones on each processor. We can skip ourself
std::vector<dof_id_type> ghost_nodes_from_proc(mesh.n_processors(), 0);
for (auto & node : mesh.node_ptr_range())
{
libmesh_assert(node);
const processor_id_type current_pid = node->processor_id();
if (current_pid != mesh.processor_id() &&
current_pid != DofObject::invalid_processor_id)
{
libmesh_assert_less (current_pid, ghost_nodes_from_proc.size());
ghost_nodes_from_proc[current_pid]++;
}
}
// We know how many objects live on each processor, so reserve()
// space for each.
for (processor_id_type pid=0; pid != mesh.n_processors(); ++pid)
requested_node_ids[pid].reserve(ghost_nodes_from_proc[pid]);
// We need to get the new pid for each node from the processor
// which *currently* owns the node. We can safely skip ourself
for (auto & node : mesh.node_ptr_range())
{
libmesh_assert(node);
const processor_id_type current_pid = node->processor_id();
if (current_pid != mesh.processor_id() &&
current_pid != DofObject::invalid_processor_id)
{
libmesh_assert_less (current_pid, requested_node_ids.size());
libmesh_assert_less (requested_node_ids[current_pid].size(),
ghost_nodes_from_proc[current_pid]);
requested_node_ids[current_pid].push_back(node->id());
}
// Unset any previously-set node processor ids
node->invalidate_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);
// For each node, set the processor ID to the min of
// its current value and this Element's processor id.
//
// TODO: we would probably get better parallel partitioning if
// we did something like "min for even numbered nodes, max for
// odd numbered". We'd need to be careful about how that would
// affect solution ordering for I/O, though.
for (unsigned int n=0; n<elem->n_nodes(); ++n)
elem->node_ptr(n)->processor_id() = std::min(elem->node_ptr(n)->processor_id(),
elem->processor_id());
}
// And loop over the subactive elements, but don't reassign
// nodes that are already active on another processor.
MeshBase::element_iterator sub_it = mesh.subactive_elements_begin();
const MeshBase::element_iterator sub_end = mesh.subactive_elements_end();
for ( ; sub_it != sub_end; ++sub_it)
{
Elem * elem = *sub_it;
libmesh_assert(elem);
libmesh_assert_not_equal_to (elem->processor_id(), DofObject::invalid_processor_id);
for (unsigned int n=0; n<elem->n_nodes(); ++n)
if (elem->node_ptr(n)->processor_id() == DofObject::invalid_processor_id)
elem->node_ptr(n)->processor_id() = elem->processor_id();
}
// Same for the inactive elements -- we will have already gotten most of these
// nodes, *except* for the case of a parent with a subset of children which are
// ghost elements. In that case some of the parent nodes will not have been
// properly handled yet
MeshBase::element_iterator not_it = mesh.not_active_elements_begin();
const MeshBase::element_iterator not_end = mesh.not_active_elements_end();
for ( ; not_it != not_end; ++not_it)
{
Elem * elem = *not_it;
libmesh_assert(elem);
libmesh_assert_not_equal_to (elem->processor_id(), DofObject::invalid_processor_id);
for (unsigned int n=0; n<elem->n_nodes(); ++n)
if (elem->node_ptr(n)->processor_id() == DofObject::invalid_processor_id)
elem->node_ptr(n)->processor_id() = elem->processor_id();
}
// 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);
// For such nodes, we'll do a sanity check later when making sure
// that we successfully reset their processor ids to something
// valid.
// Next set node ids from other processors, excluding self
for (processor_id_type p=1; p != mesh.n_processors(); ++p)
{
// Trade my requests with processor procup and procdown
processor_id_type procup = cast_int<processor_id_type>
((mesh.processor_id() + p) % mesh.n_processors());
processor_id_type procdown = cast_int<processor_id_type>
((mesh.n_processors() + mesh.processor_id() - p) %
mesh.n_processors());
std::vector<dof_id_type> request_to_fill;
mesh.comm().send_receive(procup, requested_node_ids[procup],
procdown, request_to_fill);
// Fill those requests in-place
for (std::size_t i=0; i != request_to_fill.size(); ++i)
{
Node & node = mesh.node_ref(request_to_fill[i]);
const processor_id_type new_pid = node.processor_id();
// We may have an invalid processor_id() on nodes that have been
// "detached" from coarsened-away elements but that have not yet
// themselves been removed.
// libmesh_assert_not_equal_to (new_pid, DofObject::invalid_processor_id);
// libmesh_assert_less (new_pid, mesh.n_partitions()); // this is the correct test --
request_to_fill[i] = new_pid; // the number of partitions may
} // not equal the number of processors
// Trade back the results
std::vector<dof_id_type> filled_request;
mesh.comm().send_receive(procdown, request_to_fill,
procup, filled_request);
libmesh_assert_equal_to (filled_request.size(), requested_node_ids[procup].size());
// And copy the id changes we've now been informed of
for (std::size_t i=0; i != filled_request.size(); ++i)
{
Node & node = mesh.node_ref(requested_node_ids[procup][i]);
// this is the correct test -- the number of partitions may
// not equal the number of processors
// But: we may have an invalid processor_id() on nodes that
// have been "detached" from coarsened-away elements but
// that have not yet themselves been removed.
// libmesh_assert_less (filled_request[i], mesh.n_partitions());
node.processor_id(cast_int<processor_id_type>(filled_request[i]));
}
}
#ifdef DEBUG
MeshTools::libmesh_assert_valid_procids<Node>(mesh);
#endif
}
void LocationMap<Elem>::fill(MeshBase & mesh)
{
// Populate the elem map
for (auto & elem : mesh.active_element_ptr_range())
this->insert(*elem);
}
void Partitioner::set_parent_processor_ids(MeshBase & mesh)
{
// 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 & child : mesh.active_element_ptr_range())
{
// First set descendents
std::vector<const Elem *> subactive_family;
child->total_family_tree(subactive_family);
for (std::size_t i = 0; i != subactive_family.size(); ++i)
const_cast<Elem *>(subactive_family[i])->processor_id() = child->processor_id();
// Then set ancestors
Elem * parent = child->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<const Elem *> subactive_family;
child->total_family_tree(subactive_family);
for (std::size_t i = 0; i != subactive_family.size(); ++i)
const_cast<Elem *>(subactive_family[i])->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
MeshBase::element_iterator not_it = mesh.ancestor_elements_begin();
const MeshBase::element_iterator not_end = mesh.ancestor_elements_end();
bool have_parent_in_block = false;
for ( ; not_it != not_end; ++not_it)
{
Elem * parent = *not_it;
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 (std::size_t i = 0; i != active_family.size(); ++i)
parent_pid = std::min (parent_pid, active_family[i]->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 (not_it = mesh.ancestor_elements_begin();
not_it != not_end; ++not_it)
{
Elem * parent = *not_it;
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
}