cmtkThreadPool.txx

Go to the documentation of this file.

/*
//
//  Copyright 1997-2009 Torsten Rohlfing
//  Copyright 2004-2009 SRI International
//
//  This file is part of the Computational Morphometry Toolkit.
//
//  http://www.nitrc.org/projects/cmtk/
//
//  The Computational Morphometry Toolkit is free software: you can
//  redistribute it and/or modify it under the terms of the GNU General Public
//  License as published by the Free Software Foundation, either version 3 of
//  the License, or (at your option) any later version.
//
//  The Computational Morphometry Toolkit is distributed in the hope that it
//  will be useful, but WITHOUT ANY WARRANTY; without even the implied
//  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License along
//  with the Computational Morphometry Toolkit.  If not, see
//  <http://www.gnu.org/licenses/>.
//
//  $Revision: 2398 $
//
//  $LastChangedDate: 2010-10-05 14:54:37 -0700 (Tue, 05 Oct 2010) $
//
//  $LastChangedBy: torstenrohlfing $
//
*/

#ifdef _OPENMP
#  include <omp.h>
#endif

#include <System/cmtkThreads.h>
#include <System/cmtkConsole.h>

template<class TParam> 
void
cmtk::ThreadPool::Run
( const TaskFunction taskFunction, std::vector<TParam>& taskParameters, const size_t numberOfTasksOverride )
{
  if ( ! this->m_ThreadsRunning )
    {
    this->StartThreads();
    }

  const size_t numberOfTasks = numberOfTasksOverride ? numberOfTasksOverride : taskParameters.size();
  if ( ! numberOfTasks )
    {
    StdErr << "ERROR: trying to run zero tasks on thread pool. Did you forget to resize the parameter vector?\n";
    exit( 1 );
    }

#ifdef _OPENMP
  // if OpenMP is also used in CMTK, reduce the number of OMP threads by the number of threads/tasks that we're about to run in parallel.
  const int nThreadsOMP = std::max<int>( 1, 1+Threads::GetNumberOfThreads() - std::min<int>( numberOfTasks, this->m_NumberOfThreads ) );
  omp_set_num_threads( nThreadsOMP );
#endif

#ifdef CMTK_BUILD_SMP
  // set task function
  this->m_TaskFunction = taskFunction;

  // initialize task index and count
  this->m_NumberOfTasks = numberOfTasks;
  this->m_TaskParameters.resize( this->m_NumberOfTasks );
  this->m_NextTaskIndex = 0;
  
  // set parameter pointers and post semaphores for tasks waiting to supply all running threads.
  for ( size_t idx = 0; idx < numberOfTasks; ++idx )
    {
    this->m_TaskParameters[idx] = &(taskParameters[idx]);
    }
  this->m_TaskWaitingSemaphore.Post( numberOfTasks );
  
  // now wait for all tasks to complete, as signaled via the "thread waiting" semaphore.
  for ( size_t idx = 0; idx < numberOfTasks; ++idx )
    {
    this->m_ThreadWaitingSemaphore.Wait();
    }  
#else
  // without SMP, just run everything sequentially.
  for ( size_t idx = 0; idx < numberOfTasks; ++idx )
    {
    taskFunction( &taskParameters[idx], idx, numberOfTasks, 0, 1 );
    }
#endif

#ifdef _OPENMP
  // restore OpenMP thread count to maximum
  omp_set_num_threads( Threads::GetNumberOfThreads() );
#endif
}