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MatrixFree setup: Reduce cost of vector access pattern computation #15867

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Aug 11, 2023
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MatrixFree setup: Reduce cost of vector access pattern computation #15867

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86 changes: 38 additions & 48 deletions include/deal.II/matrix_free/dof_info.templates.h
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Original file line number Diff line number Diff line change
Expand Up @@ -389,23 +389,55 @@ namespace internal
std::vector<unsigned int> touched_last_by(
(n_dofs + chunk_size_zero_vector - 1) / chunk_size_zero_vector,
numbers::invalid_unsigned_int);
std::vector<unsigned int> cells_in_interval;
for (unsigned int part = 0;
part < task_info.partition_row_index.size() - 2;
++part)
for (unsigned int chunk = task_info.partition_row_index[part];
chunk < task_info.partition_row_index[part + 1];
++chunk)
{
cells_in_interval.clear();
for (unsigned int cell = task_info.cell_partition_data[chunk];
cell < task_info.cell_partition_data[chunk + 1];
++cell)
for (unsigned int v = 0; v < vectorization_length; ++v)
cells_in_interval.push_back(cell * vectorization_length + v);
if (faces.size() > 0)
{
for (unsigned int face = task_info.face_partition_data[chunk];
face < task_info.face_partition_data[chunk + 1];
++face)
for (unsigned int v = 0; v < vectorization_length; ++v)
{
if (faces[face].cells_interior[v] !=
numbers::invalid_unsigned_int)
cells_in_interval.push_back(
faces[face].cells_interior[v]);
if (faces[face].cells_exterior[v] !=
numbers::invalid_unsigned_int)
cells_in_interval.push_back(
faces[face].cells_exterior[v]);
}
for (unsigned int face =
task_info.boundary_partition_data[chunk];
face < task_info.boundary_partition_data[chunk + 1];
++face)
for (unsigned int v = 0; v < vectorization_length; ++v)
if (faces[face].cells_interior[v] !=
numbers::invalid_unsigned_int)
cells_in_interval.push_back(
faces[face].cells_interior[v]);
}
std::sort(cells_in_interval.begin(), cells_in_interval.end());
cells_in_interval.erase(std::unique(cells_in_interval.begin(),
cells_in_interval.end()),
cells_in_interval.end());

for (const unsigned int cell : cells_in_interval)
{
for (unsigned int it =
row_starts[cell * vectorization_length * n_components]
.first;
it != row_starts[(cell + 1) * vectorization_length *
n_components]
.first;
for (unsigned int it = row_starts[cell * n_components].first;
it != row_starts[(cell + 1) * n_components].first;
++it)
{
const unsigned int myindex =
Expand All @@ -416,48 +448,6 @@ namespace internal
touched_last_by[myindex] = chunk;
}
}
if (faces.size() > 0)
{
const auto fill_touched_by_for_face =
[&](const unsigned int face) {
for (unsigned int v = 0; v < length; ++v)
{
const auto fill_touched_by_for_cell =
[&](const unsigned cell) {
if (cell == numbers::invalid_unsigned_int)
return;
for (unsigned int it =
row_starts[cell * n_components].first;
it !=
row_starts[(cell + 1) * n_components].first;
++it)
{
const unsigned int myindex =
dof_indices[it] / chunk_size_zero_vector;
if (touched_first_by[myindex] ==
numbers::invalid_unsigned_int)
touched_first_by[myindex] = chunk;
touched_last_by[myindex] = chunk;
}
};

fill_touched_by_for_cell(faces[face].cells_interior[v]);
fill_touched_by_for_cell(faces[face].cells_exterior[v]);
}
};

for (unsigned int face = task_info.face_partition_data[chunk];
face < task_info.face_partition_data[chunk + 1];
++face)
fill_touched_by_for_face(face);


for (unsigned int face =
task_info.boundary_partition_data[chunk];
face < task_info.boundary_partition_data[chunk + 1];
++face)
fill_touched_by_for_face(face);
}
}

// ensure that all indices are touched at least during the last round
Expand Down