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/*
//
// Copyright 1997-2009 Torsten Rohlfing
//
// Copyright 2004-2011 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: 5436 $
//
// $LastChangedDate: 2018-12-10 19:01:20 -0800 (Mon, 10 Dec 2018) $
//
// $LastChangedBy: torstenrohlfing $
//
*/
#ifndef __cmtkThreads_h_included_
#define __cmtkThreads_h_included_
#include <cmtkconfig.h>
#include <stdlib.h>
#include <stdio.h>
#include <vector>
#include <algorithm>
#include <System/cmtkThreadSystemTypes.h>
#include <System/cmtkThreadParameters.h>
namespace
cmtk
{
/** \addtogroup System */
//@{
/** Thread-related utility functions and global configuration variables.
*/
namespace
Threads
{
/// Check environment variables that control thread creation.
void CheckEnvironment();
/// Check whether this system supports threads.
bool Available();
/// Number of threads to run in parallel.
extern int GetNumberOfThreads();
/** Set the number of threads to run in parallel.
* If the given parameter is less than or equal to zero, the number of
* threads is set to equal the number of currently available CPUs. This also
* applies when this function is called without any parameter.
*\param numberOfThreads Number of parallel threads to run. This is a
* maximum value. Particular tasks may execute with less parallel threads
* than this value.
*\param force If this flag is off (default), then the number of parallel
* threads is limited by the number of available CPUs on the current host.
* If the flag is true, the limitation is not entirely lifted, but the
* number of threads is limited by the maximum number of threads that
* can be created by a process on the current operating system.
*\return The actual number of threads that the library was set to.
*/
extern int SetNumberOfThreads( const int numberOfThreads, const bool force = false );
/// Helper function for setting number of threads from command line.
extern void SetNumberOfThreads( const long int numberOfThreads );
/// Return number of threads allowed per process on this system.
extern int GetMaxThreads();
/// Return number of processors currently online.
extern int GetNumberOfProcessors();
/// (Maximum) number of threads to run in parallel.
extern int NumberOfThreads;
/** Specialized but more hands-on thread scheduling function.
*\param threadCall Thread function to be called.
*\param numberOfThreads Number of parallel threads. This parameter must not
* exceed the number of threads set using and returned by SetNumberOfThreads.
*\param parameters Pointer to an array of parameter blocks for all parallel
* threads.
*\param parameterSize Size in bytes of each thread parameter block in the
* array pointed to by the previous parameter.
*/
void RunThreads( ThreadFunction threadCall, const unsigned numberOfThreads, void *const parameters, const size_t parameterSize );
/** Generic thread scheduling function.
* This function created a given number of parallel threads with
* user-provided thread-specific parameters. It then waits for all threads
* to complete before returning. This function is a convenience wrapper for
* the four-parameter function of the same name.
*\param threadCall Thread function to be called.
*\param numberOfThreads Number of parallel threads. This parameter must not
* exceed the number of threads set using and returned by SetNumberOfThreads.
*\param parameters Pointer to an array of parameter blocks for all parallel
* threads. This is a template type parameter, so arbitrary parameter blocks
* can be used.
*/
template<class T> void RunThreads( ThreadFunction threadCall, const unsigned numberOfThreads, T *const parameters )
{
Threads::RunThreads( threadCall, numberOfThreads, parameters, sizeof( T ) );
}
/** Compute stride for threaded loops.
* This class computes stride and loop start and ends for threaded loops, based on
* a trade-off between number of CPUs in the system and total loop iterations.
*/
class Stride
{
public:
/// Constructor: compute stride based on 2 blocks per available CPU.
Stride( const size_t totalIterations )
: m_TotalIterations( totalIterations )
{
this->m_Stride = this->m_TotalIterations / (2 * cmtk::Threads::GetNumberOfProcessors() );
this->m_Blocks = ((this->m_TotalIterations-1) / this->m_Stride) + 1;
}
/// Return number of blocks.
size_t NBlocks() const
{
return this->m_Blocks;
}
/// Loop "from" for a given block.
size_t From( const size_t blockIdx ) const
{
return blockIdx * this->m_Stride;
}
size_t To( const size_t blockIdx ) const
{
return std::min( (1+blockIdx) * this->m_Stride, this->m_TotalIterations );
}
private:
/// Total number of loop iterations.
size_t m_TotalIterations;
/// Number of blocks.
size_t m_Blocks;
/// Stride.
size_t m_Stride;
};
} // namespace Threads
//@}
} // namespace cmtk
#endif // #ifndef __cmtkThreads_h_included_
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