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/*=========================================================================
Program: Visualization Toolkit
Module: vtkSMPToolsImpl.cxx
Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.
See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notice for more information.
=========================================================================*/
#include "SMP/Common/vtkSMPToolsImpl.h"
#include "SMP/OpenMP/vtkSMPToolsImpl.txx"
#include <cstdlib> // For std::getenv()
#include <omp.h>
#include <stack> // For std::stack
namespace vtk
{
namespace detail
{
namespace smp
{
VTK_ABI_NAMESPACE_BEGIN
static int specifiedNumThreads = 0;
static std::stack<int> threadIdStack;
//------------------------------------------------------------------------------
template <>
void vtkSMPToolsImpl<BackendType::OpenMP>::Initialize(int numThreads)
{
const int maxThreads = omp_get_max_threads();
if (numThreads == 0)
{
const char* vtkSmpNumThreads = std::getenv("VTK_SMP_MAX_THREADS");
if (vtkSmpNumThreads)
{
numThreads = std::atoi(vtkSmpNumThreads);
}
else if (specifiedNumThreads)
{
specifiedNumThreads = 0;
omp_set_num_threads(maxThreads);
}
}
#pragma omp single
if (numThreads > 0)
{
numThreads = std::min(numThreads, maxThreads);
specifiedNumThreads = numThreads;
omp_set_num_threads(numThreads);
}
}
//------------------------------------------------------------------------------
int GetNumberOfThreadsOpenMP()
{
return specifiedNumThreads ? specifiedNumThreads : omp_get_max_threads();
}
//------------------------------------------------------------------------------
bool GetSingleThreadOpenMP()
{
return threadIdStack.top() == omp_get_thread_num();
}
//------------------------------------------------------------------------------
template <>
int vtkSMPToolsImpl<BackendType::OpenMP>::GetEstimatedNumberOfThreads()
{
return GetNumberOfThreadsOpenMP();
}
//------------------------------------------------------------------------------
template <>
bool vtkSMPToolsImpl<BackendType::OpenMP>::GetSingleThread()
{
return GetSingleThreadOpenMP();
}
//------------------------------------------------------------------------------
void vtkSMPToolsImplForOpenMP(vtkIdType first, vtkIdType last, vtkIdType grain,
ExecuteFunctorPtrType functorExecuter, void* functor, bool nestedActivated)
{
if (grain <= 0)
{
vtkIdType estimateGrain = (last - first) / (GetNumberOfThreadsOpenMP() * 4);
grain = (estimateGrain > 0) ? estimateGrain : 1;
}
omp_set_nested(nestedActivated);
#pragma omp single
threadIdStack.emplace(omp_get_thread_num());
#pragma omp parallel for schedule(runtime)
for (vtkIdType from = first; from < last; from += grain)
{
functorExecuter(functor, from, grain, last);
}
#pragma omp single
threadIdStack.pop();
}
VTK_ABI_NAMESPACE_END
} // namespace smp
} // namespace detail
} // namespace vtk
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