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Avoid unnecessary locally_relevant_dofs in mg_transfer_internal #14020

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Jun 28, 2022
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Avoid unnecessary locally_relevant_dofs in mg_transfer_internal #14020

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69766ec
Use alias for locally owned index sets
kronbichler Jun 20, 2022
7dbfee3
Avoid unnecessary locally_relevant_dofs in mg_transfer_internal
kronbichler Jun 20, 2022
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81 changes: 31 additions & 50 deletions source/multigrid/mg_transfer_internal.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -88,16 +88,17 @@ namespace internal
copy_indices.resize(n_levels);
copy_indices_global_mine.resize(n_levels);
copy_indices_level_mine.resize(n_levels);
IndexSet globally_relevant;
DoFTools::extract_locally_relevant_dofs(dof_handler, globally_relevant);
const IndexSet &owned_dofs = dof_handler.locally_owned_dofs();

const unsigned int dofs_per_cell = dof_handler.get_fe().n_dofs_per_cell();
std::vector<types::global_dof_index> global_dof_indices(dofs_per_cell);
std::vector<types::global_dof_index> level_dof_indices(dofs_per_cell);

for (unsigned int level = 0; level < n_levels; ++level)
{
std::vector<bool> dof_touched(globally_relevant.n_elements(), false);
std::vector<bool> dof_touched(owned_dofs.n_elements(), false);
const IndexSet & owned_level_dofs =
dof_handler.locally_owned_mg_dofs(level);

// for the most common case where copy_indices are locally owned
// both globally and on the level, we want to skip collecting pairs
Expand All @@ -119,9 +120,8 @@ namespace internal
numbers::artificial_subdomain_id))
continue;

unrolled_copy_indices.resize(
dof_handler.locally_owned_dofs().n_elements(),
numbers::invalid_dof_index);
unrolled_copy_indices.resize(owned_dofs.n_elements(),
numbers::invalid_dof_index);

// get the dof numbers of this cell for the global and the
// level-wise numbering
Expand All @@ -141,53 +141,36 @@ namespace internal
// and the level one. This check involves locally owned
// indices which often consist only of a single range, so
// they are cheap to look up.
const types::global_dof_index global_index_in_set =
owned_dofs.index_within_set(global_dof_indices[i]);
bool global_mine =
dof_handler.locally_owned_dofs().is_element(
global_dof_indices[i]);
global_index_in_set != numbers::invalid_dof_index;
bool level_mine =
dof_handler.locally_owned_mg_dofs(level).is_element(
level_dof_indices[i]);
owned_level_dofs.is_element(level_dof_indices[i]);

if (global_mine && level_mine)
{
// we own both the active dof index and the level one ->
// set them into the vector, indexed by the local index
// range of the active dof
unrolled_copy_indices[dof_handler.locally_owned_dofs()
.index_within_set(
global_dof_indices[i])] =
unrolled_copy_indices[global_index_in_set] =
level_dof_indices[i];
}
else if (global_mine &&
dof_touched[global_index_in_set] == false)
{
copy_indices_global_mine[level].emplace_back(
global_dof_indices[i], level_dof_indices[i]);

// send this to the owner of the level_dof:
send_data_temp.emplace_back(level,
global_dof_indices[i],
level_dof_indices[i]);
dof_touched[global_index_in_set] = true;
}
else
{
// Get the relevant dofs index - this might be more
// expensive to look up than the active indices, so we
// only do it for the local-remote case within this loop.
const types::global_dof_index relevant_idx =
globally_relevant.index_within_set(
global_dof_indices[i]);

// Work on this dof if we haven't already (on this or a
// coarser level)
if (dof_touched[relevant_idx] == false)
{
if (global_mine)
{
copy_indices_global_mine[level].emplace_back(
global_dof_indices[i], level_dof_indices[i]);

// send this to the owner of the level_dof:
send_data_temp.emplace_back(level,
global_dof_indices[i],
level_dof_indices[i]);
}
else
{
// somebody will send those to me
}

dof_touched[relevant_idx] = true;
}
// somebody will send those to me
}
}
}
Expand All @@ -203,14 +186,13 @@ namespace internal
if (copy_indices_global_mine[level].empty())
copy_indices[level].reserve(unrolled_copy_indices.size());

// locally_owned_dofs().nth_index_in_set(i) in this query is
// owned_dofs.nth_index_in_set(i) in this query is
// usually cheap to look up as there are few ranges in
// dof_handler.locally_owned_dofs()
// the locally owned part
for (unsigned int i = 0; i < unrolled_copy_indices.size(); ++i)
if (unrolled_copy_indices[i] != numbers::invalid_dof_index)
copy_indices[level].emplace_back(
dof_handler.locally_owned_dofs().nth_index_in_set(i),
unrolled_copy_indices[i]);
owned_dofs.nth_index_in_set(i), unrolled_copy_indices[i]);
}
}

Expand Down Expand Up @@ -260,7 +242,7 @@ namespace internal

for (unsigned int level = 0; level < n_levels; ++level)
{
const IndexSet &is_local =
const IndexSet &owned_level_dofs =
dof_handler.locally_owned_mg_dofs(level);

std::vector<types::global_dof_index> level_dof_indices;
Expand All @@ -272,15 +254,15 @@ namespace internal
global_dof_indices.push_back(dofpair.global_dof_index);
}

IndexSet is_ghost(is_local.size());
IndexSet is_ghost(owned_level_dofs.size());
is_ghost.add_indices(level_dof_indices.begin(),
level_dof_indices.end());

AssertThrow(level_dof_indices.size() == is_ghost.n_elements(),
ExcMessage("Size does not match!"));

const auto index_owner =
Utilities::MPI::compute_index_owner(is_local,
Utilities::MPI::compute_index_owner(owned_level_dofs,
is_ghost,
tria->get_communicator());

Expand Down Expand Up @@ -691,8 +673,7 @@ namespace internal
setup_element_info(elem_info, *fe, dof_handler);


// -------------- 2. Extract and match dof indices between child and
// parent
// ---------- 2. Extract and match dof indices between child and parent
const unsigned int n_levels = tria.n_global_levels();
level_dof_indices.resize(n_levels);
parent_child_connect.resize(n_levels - 1);
Expand Down