/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkSMPToolsInternal.h.in

  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.

=========================================================================*/

#ifndef vtkSMPToolsInternal_h
#define vtkSMPToolsInternal_h

#include "vtkCommonCoreModule.h"       // For export macro
#include "vtkSMPToolsInternalCommon.h" // For common vtk smp class

#ifdef _MSC_VER
#pragma push_macro("__TBB_NO_IMPLICIT_LINKAGE")
#define __TBB_NO_IMPLICIT_LINKAGE 1
#endif

#include <tbb/blocked_range.h>
#include <tbb/parallel_for.h>
#include <tbb/parallel_sort.h>

#ifdef _MSC_VER
#pragma pop_macro("__TBB_NO_IMPLICIT_LINKAGE")
#endif

namespace vtk
{
namespace detail
{
namespace smp
{

typedef void (*ExecuteFunctorPtrType)(void*, vtkIdType, vtkIdType, vtkIdType);
void VTKCOMMONCORE_EXPORT vtkSMPTools_Impl_For_TBB(vtkIdType first, vtkIdType last, vtkIdType grain,
  ExecuteFunctorPtrType functorExecuter, void* functor);

//--------------------------------------------------------------------------------
template <typename T>
class FuncCall
{
  T& o;

  void operator=(const FuncCall&) = delete;

public:
  void operator()(const tbb::blocked_range<vtkIdType>& r) const { o.Execute(r.begin(), r.end()); }

  FuncCall(T& _o)
    : o(_o)
  {
  }
};

//--------------------------------------------------------------------------------
template <typename FunctorInternal>
void ExecuteFunctor(void* functor, vtkIdType first, vtkIdType last, vtkIdType grain)
{
  FunctorInternal& fi = *reinterpret_cast<FunctorInternal*>(functor);

  vtkIdType range = last - first;
  if (range <= 0)
  {
    return;
  }
  if (grain > 0)
  {
    tbb::parallel_for(
      tbb::blocked_range<vtkIdType>(first, last, grain), FuncCall<FunctorInternal>(fi));
  }
  else
  {
    // When the grain is not specified, automatically calculate an appropriate grain size so
    // most of the time will still be spent running the calculation and not task overhead.

    // Estimate of how many threads we might be able to run
    const vtkIdType numberThreadsEstimate = 40;
    // Plan for a few batches per thread so one busy core doesn't stall the whole system
    const vtkIdType batchesPerThread = 5;
    const vtkIdType batches = numberThreadsEstimate * batchesPerThread;

    if (range >= batches)
    {
      // std::ceil round up for systems without cmath
      vtkIdType calculatedGrain = ((range - 1) / batches) + 1;
      tbb::parallel_for(
        tbb::blocked_range<vtkIdType>(first, last, calculatedGrain), FuncCall<FunctorInternal>(fi));
    }
    else
    {
      // Data is too small to generate a reasonable grain. Fallback to default so data still runs
      // on as many threads as possible (Jan 2020: Default is one index per tbb task).
      tbb::parallel_for(tbb::blocked_range<vtkIdType>(first, last), FuncCall<FunctorInternal>(fi));
    }
  }
}

//--------------------------------------------------------------------------------
template <typename FunctorInternal>
void vtkSMPTools_Impl_For(vtkIdType first, vtkIdType last, vtkIdType grain, FunctorInternal& fi)
{
  vtkSMPTools_Impl_For_TBB(first, last, grain, ExecuteFunctor<FunctorInternal>, &fi);
}

//--------------------------------------------------------------------------------
template <typename InputIt, typename OutputIt, typename Functor>
void vtkSMPTools_Impl_Transform(
  InputIt inBegin, InputIt inEnd, OutputIt outBegin, Functor transform)
{
  auto size = std::distance(inBegin, inEnd);

  UnaryTransformCall<InputIt, OutputIt, Functor> exec(inBegin, outBegin, transform);
  vtkSMPTools_Impl_For(0, size, 0, exec);
}

//--------------------------------------------------------------------------------
template <typename InputIt1, typename InputIt2, typename OutputIt, typename Functor>
static void vtkSMPTools_Impl_Transform(
  InputIt1 inBegin1, InputIt1 inEnd, InputIt2 inBegin2, OutputIt outBegin, Functor transform)
{
  auto size = std::distance(inBegin1, inEnd);

  BinaryTransformCall<InputIt1, InputIt2, OutputIt, Functor> exec(
    inBegin1, inBegin2, outBegin, transform);
  vtkSMPTools_Impl_For(0, size, 0, exec);
}

//--------------------------------------------------------------------------------
template <typename Iterator, typename T>
void vtkSMPTools_Impl_Fill(Iterator begin, Iterator end, const T& value)
{
  auto size = std::distance(begin, end);

  FillFunctor<T> fill(value);
  UnaryTransformCall<Iterator, Iterator, FillFunctor<T>> exec(begin, begin, fill);
  vtkSMPTools_Impl_For(0, size, 0, exec);
}

//--------------------------------------------------------------------------------
template <typename RandomAccessIterator>
void vtkSMPTools_Impl_Sort(RandomAccessIterator begin, RandomAccessIterator end)
{
  tbb::parallel_sort(begin, end);
}

//--------------------------------------------------------------------------------
template <typename RandomAccessIterator, typename Compare>
void vtkSMPTools_Impl_Sort(RandomAccessIterator begin, RandomAccessIterator end, Compare comp)
{
  tbb::parallel_sort(begin, end, comp);
}

} // namespace smp
} // namespace detail
} // namespace vtk

#endif
