itkDomainThreader.hxx

/*=========================================================================
 *
 *  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 itkDomainThreader_hxx
#define itkDomainThreader_hxx


namespace itk
{

template <typename TDomainPartitioner, typename TAssociate>
DomainThreader<TDomainPartitioner, TAssociate>::DomainThreader()
  : m_Associate(nullptr)

{
  this->m_DomainPartitioner = DomainPartitionerType::New();
  this->m_MultiThreader = MultiThreaderBase::New();
  this->m_NumberOfWorkUnits = this->m_MultiThreader->GetNumberOfWorkUnits();
}

template <typename TDomainPartitioner, typename TAssociate>
MultiThreaderBase *
DomainThreader<TDomainPartitioner, TAssociate>::GetMultiThreader() const
{
  return this->m_MultiThreader;
}

template <typename TDomainPartitioner, typename TAssociate>
void
DomainThreader<TDomainPartitioner, TAssociate>::SetMaximumNumberOfThreads(const ThreadIdType threads)
{
  if (threads != this->GetMaximumNumberOfThreads())
  {
    this->m_MultiThreader->SetMaximumNumberOfThreads(threads);
    this->Modified();
  }
}

template <typename TDomainPartitioner, typename TAssociate>
void
DomainThreader<TDomainPartitioner, TAssociate>::Execute(TAssociate * enclosingClass, const DomainType & completeDomain)
{
  this->m_Associate = enclosingClass;
  this->m_CompleteDomain = completeDomain;

  this->DetermineNumberOfWorkUnitsUsed();

  this->BeforeThreadedExecution();

  // This calls ThreadedExecution in each thread.
  this->StartThreadingSequence();

  this->AfterThreadedExecution();
}

template <typename TDomainPartitioner, typename TAssociate>
void
DomainThreader<TDomainPartitioner, TAssociate>::DetermineNumberOfWorkUnitsUsed()
{
  ThreadIdType numberOfWorkUnits = this->GetNumberOfWorkUnits();

  // Attempt a single dummy partition, just to get the number of subdomains actually created
  DomainType subdomain;
  this->m_NumberOfWorkUnitsUsed =
    this->m_DomainPartitioner->PartitionDomain(0, numberOfWorkUnits, this->m_CompleteDomain, subdomain);

  this->GetMultiThreader()->SetNumberOfWorkUnits(this->m_NumberOfWorkUnitsUsed);

  if (this->m_NumberOfWorkUnitsUsed > numberOfWorkUnits)
  {
    itkExceptionMacro(
      "A subclass of ThreadedDomainPartitioner::PartitionDomain returned more subdomains than were requested");
  }
}

template <typename TDomainPartitioner, typename TAssociate>
void
DomainThreader<TDomainPartitioner, TAssociate>::StartThreadingSequence()
{
  // Set up the multithreaded processing
  ThreadStruct str;
  str.domainThreader = this;

  this->GetMultiThreader()->SetSingleMethodAndExecute(this->ThreaderCallback, &str);
}

template <typename TDomainPartitioner, typename TAssociate>
ITK_THREAD_RETURN_FUNCTION_CALL_CONVENTION
DomainThreader<TDomainPartitioner, TAssociate>::ThreaderCallback(void * arg)
{
  auto *             info = static_cast<MultiThreaderBase::WorkUnitInfo *>(arg);
  auto *             str = static_cast<ThreadStruct *>(info->UserData);
  DomainThreader *   thisDomainThreader = str->domainThreader;
  const ThreadIdType workUnitID = info->WorkUnitID;
  const ThreadIdType workUnitCount = info->NumberOfWorkUnits;

  // Get the sub-domain to process for this thread.
  DomainType         subdomain;
  const ThreadIdType total = thisDomainThreader->GetDomainPartitioner()->PartitionDomain(
    workUnitID, workUnitCount, thisDomainThreader->m_CompleteDomain, subdomain);

  // Execute the actual method with appropriate sub-domain.
  // If the work unit ID is greater than the total number of regions
  // that PartitionDomain will create, don't use this thread.
  // Sometimes the threads don't break up very well and it is just
  // as efficient to leave a few threads idle.
  if (workUnitID < total)
  {
    thisDomainThreader->ThreadedExecution(subdomain, workUnitID);
  }

  return ITK_THREAD_RETURN_DEFAULT_VALUE;
}
} // namespace itk

#endif