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itkThreadedIteratorRangePartitioner.hxx
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itkThreadedIteratorRangePartitioner.hxx
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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkThreadedIteratorRangePartitioner_hxx
#define itkThreadedIteratorRangePartitioner_hxx
#include "itkNumericTraits.h"
#include "itkMath.h"
#include <iterator>
namespace itk
{
template <typename TIterator>
ThreadIdType
ThreadedIteratorRangePartitioner<TIterator>::PartitionDomain(const ThreadIdType threadId,
const ThreadIdType requestedTotal,
const DomainType & completeDomain,
DomainType & subDomain) const
{
// overallIndexRange is expected to be inclusive
// determine the actual number of pieces that will be generated
ThreadIdType count = std::distance(completeDomain.Begin(), completeDomain.End());
auto valuesPerThread = Math::Ceil<ThreadIdType>(static_cast<double>(count) / static_cast<double>(requestedTotal));
ThreadIdType maxThreadIdUsed =
Math::Ceil<ThreadIdType>(static_cast<double>(count) / static_cast<double>(valuesPerThread)) - 1;
if (threadId > maxThreadIdUsed)
{
// return before advancing Begin iterator, to prevent advancing
// past end
return maxThreadIdUsed + 1;
}
const ThreadIdType startIndexCount = threadId * valuesPerThread;
subDomain.m_Begin = completeDomain.Begin();
std::advance(subDomain.m_Begin, startIndexCount);
if (threadId < maxThreadIdUsed)
{
subDomain.m_End = subDomain.m_Begin;
std::advance(subDomain.m_End, valuesPerThread);
}
if (threadId == maxThreadIdUsed)
{
// last thread needs to process the "rest" of the range
subDomain.m_End = completeDomain.End();
}
return maxThreadIdUsed + 1;
}
} // end namespace itk
#endif