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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2009 - 2025 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Part of the source code is dual licensed under Apache-2.0 WITH
// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
// governing the source code and code contributions can be found in
// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
//
// ------------------------------------------------------------------------
#include <deal.II/base/exceptions.h>
#include <deal.II/base/parallel.h>
#ifdef DEAL_II_WITH_TASKFLOW
# include <deal.II/base/multithread_info.h>
# include <taskflow/algorithm/for_each.hpp>
# include <taskflow/taskflow.hpp>
#endif
#ifdef DEAL_II_WITH_TBB
# include <tbb/blocked_range.h>
# include <tbb/parallel_for.h>
# include <tbb/parallel_reduce.h>
# include <tbb/partitioner.h>
#else
# include <boost/range/iterator_range.hpp>
#endif
DEAL_II_NAMESPACE_OPEN
namespace internal
{
namespace VectorImplementation
{
// set minimum grain size. this value has been determined by experiments
// with the actual dealii::Vector implementation and takes vectorization
// that is done inside most functions of dealii::Vector into account
// (without vectorization, we would land at around 1000). for smaller
// values than this, the scheduling overhead will be significant. if the
// value becomes too large, on the other hand, the work load cannot be
// split into enough chunks and the problem becomes badly balanced. the
// tests are documented at https://github.com/dealii/dealii/issues/2496
unsigned int minimum_parallel_grain_size = 4096;
} // namespace VectorImplementation
namespace SparseMatrixImplementation
{
// set this value to 1/16 of the value of the minimum grain size of
// vectors (a factor of 4 because we assume that sparse matrix-vector
// products do not vectorize and the other factor of 4 because we expect
// at least four entries per row). this rests on the fact that we have to
// do a lot more work per row of a matrix than per element of a vector. it
// could possibly be reduced even further but that doesn't appear worth it
// any more for anything but very small matrices that we don't care that
// much about anyway.
unsigned int minimum_parallel_grain_size = 256;
} // namespace SparseMatrixImplementation
} // namespace internal
namespace parallel
{
namespace internal
{
#ifdef DEAL_II_WITH_TBB
TBBPartitioner::TBBPartitioner()
: my_partitioner(std::make_shared<tbb::affinity_partitioner>())
, in_use(false)
{}
TBBPartitioner::~TBBPartitioner()
{
AssertNothrow(in_use == false,
ExcInternalError(
"A vector partitioner goes out of scope, but "
"it appears to be still in use."));
}
std::shared_ptr<tbb::affinity_partitioner>
TBBPartitioner::acquire_one_partitioner()
{
std::lock_guard<std::mutex> lock(mutex);
if (in_use)
return std::make_shared<tbb::affinity_partitioner>();
in_use = true;
return my_partitioner;
}
void
TBBPartitioner::release_one_partitioner(
const std::shared_ptr<tbb::affinity_partitioner> &p)
{
if (p.get() == my_partitioner.get())
{
std::lock_guard<std::mutex> lock(mutex);
in_use = false;
}
}
#else
TBBPartitioner::TBBPartitioner() = default;
#endif
} // namespace internal
} // namespace parallel
DEAL_II_NAMESPACE_CLOSE
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