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//                        Kokkos v. 2.0
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#ifndef KOKKOS_IMPL_OPENMP_TASK_HPP
#define KOKKOS_IMPL_OPENMP_TASK_HPP

#if defined( KOKKOS_ENABLE_TASKPOLICY )

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

namespace Kokkos {
namespace Impl {

template<>
class TaskQueueSpecialization< Kokkos::Experimental::OpenMPTarget >
{
public:

  using execution_space = Kokkos::Experimental::OpenMPTarget ;
  using queue_type      = Kokkos::Impl::TaskQueue< execution_space > ;
  using task_base_type  = Kokkos::Impl::TaskBase< execution_space , void , void > ;

  // Must specify memory space
  using memory_space = Kokkos::HostSpace ;

  static
  void iff_single_thread_recursive_execute( queue_type * const );

  // Must provide task queue execution function
  static void execute( queue_type * const );

  // Must provide mechanism to set function pointer in
  // execution space from the host process.
  template< typename FunctorType >
  static
  void proc_set_apply( task_base_type::function_type * ptr )
    {
      using TaskType = TaskBase< Kokkos::Experimental::OpenMPTarget
                               , typename FunctorType::value_type
                               , FunctorType
                               > ;
       *ptr = TaskType::apply ;
    }
};

extern template class TaskQueue< Kokkos::Experimental::OpenMPTarget > ;

//----------------------------------------------------------------------------

template<>
class TaskExec< Kokkos::Experimental::OpenMPTarget >
{
private:

  TaskExec( TaskExec && ) = delete ;
  TaskExec( TaskExec const & ) = delete ;
  TaskExec & operator = ( TaskExec && ) = delete ;
  TaskExec & operator = ( TaskExec const & ) = delete ;


  using PoolExec = Kokkos::Impl::OpenMPTargetExec ;

  friend class Kokkos::Impl::TaskQueue< Kokkos::Experimental::OpenMPTarget > ;
  friend class Kokkos::Impl::TaskQueueSpecialization< Kokkos::Experimental::OpenMPTarget > ;

  PoolExec * const m_self_exec ;  ///< This thread's thread pool data structure 
  PoolExec * const m_team_exec ;  ///< Team thread's thread pool data structure
  int64_t          m_sync_mask ;
  int64_t mutable  m_sync_value ;
  int     mutable  m_sync_step ;
  int              m_group_rank ; ///< Which "team" subset of thread pool
  int              m_team_rank ;  ///< Which thread within a team
  int              m_team_size ;

  TaskExec();
  TaskExec( PoolExec & arg_exec , int arg_team_size );

  void team_barrier_impl() const ;

public:

#if defined( KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST )
  void * team_shared() const
    { return m_team_exec ? m_team_exec->scratch_thread() : (void*) 0 ; }

  int team_shared_size() const
    { return m_team_exec ? m_team_exec->scratch_thread_size() : 0 ; }

  /**\brief  Whole team enters this function call
   *         before any teeam member returns from
   *         this function call.
   */
  void team_barrier() const { if ( 1 < m_team_size ) team_barrier_impl(); }
#else
  KOKKOS_INLINE_FUNCTION void team_barrier() const {}
  KOKKOS_INLINE_FUNCTION void * team_shared() const { return 0 ; }
  KOKKOS_INLINE_FUNCTION int team_shared_size() const { return 0 ; }
#endif

  KOKKOS_INLINE_FUNCTION
  int team_rank() const { return m_team_rank ; }

  KOKKOS_INLINE_FUNCTION
  int team_size() const { return m_team_size ; }
};

}} /* namespace Kokkos::Impl */

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

namespace Kokkos {

template<typename iType>
KOKKOS_INLINE_FUNCTION
Impl::TeamThreadRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >
TeamThreadRange
  ( Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > & thread
  , const iType & count )
{
  return Impl::TeamThreadRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >(thread,count);
}

template<typename iType>
KOKKOS_INLINE_FUNCTION
Impl::TeamThreadRangeBoundariesStruct<iType,Impl:: TaskExec< Kokkos::Experimental::OpenMPTarget > >
TeamThreadRange
  ( Impl:: TaskExec< Kokkos::Experimental::OpenMPTarget > & thread
  , const iType & start
  , const iType & end )
{
  return Impl::TeamThreadRangeBoundariesStruct<iType,Impl:: TaskExec< Kokkos::Experimental::OpenMPTarget > >(thread,start,end);
}

/** \brief  Inter-thread parallel_for. Executes lambda(iType i) for each i=0..N-1.
 *
 * The range i=0..N-1 is mapped to all threads of the the calling thread team.
 * This functionality requires C++11 support.
*/
template<typename iType, class Lambda>
KOKKOS_INLINE_FUNCTION
void parallel_for
  ( const Impl::TeamThreadRangeBoundariesStruct<iType,Impl:: TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries
  , const Lambda& lambda
  )
{
  for( iType i = loop_boundaries.start; i < loop_boundaries.end; i+=loop_boundaries.increment) {
    lambda(i);
  }
}

template<typename iType, class Lambda, typename ValueType>
KOKKOS_INLINE_FUNCTION
void parallel_reduce
  ( const Impl::TeamThreadRangeBoundariesStruct<iType,Impl:: TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries
  , const Lambda& lambda
  , ValueType& initialized_result)
{
  int team_rank = loop_boundaries.thread.team_rank(); // member num within the team
  ValueType result = initialized_result;

  for( iType i = loop_boundaries.start; i < loop_boundaries.end; i+=loop_boundaries.increment) {
    lambda(i, result);
  }

  if ( 1 < loop_boundaries.thread.team_size() ) {

    ValueType *shared = (ValueType*) loop_boundaries.thread.team_shared();

    loop_boundaries.thread.team_barrier();
    shared[team_rank] = result;

    loop_boundaries.thread.team_barrier();

    // reduce across threads to thread 0
    if (team_rank == 0) {
      for (int i = 1; i < loop_boundaries.thread.team_size(); i++) {
        shared[0] += shared[i];
      }
    }

    loop_boundaries.thread.team_barrier();

    // broadcast result
    initialized_result = shared[0];
  }
  else {
    initialized_result = result ;
  }
}

template< typename iType, class Lambda, typename ValueType, class JoinType >
KOKKOS_INLINE_FUNCTION
void parallel_reduce
  (const Impl::TeamThreadRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries,
   const Lambda & lambda,
   const JoinType & join,
   ValueType& initialized_result)
{
  int team_rank = loop_boundaries.thread.team_rank(); // member num within the team
  ValueType result = initialized_result;

  for( iType i = loop_boundaries.start; i < loop_boundaries.end; i+=loop_boundaries.increment) {
    lambda(i, result);
  }

  if ( 1 < loop_boundaries.thread.team_size() ) {
    ValueType *shared = (ValueType*) loop_boundaries.thread.team_shared();

    loop_boundaries.thread.team_barrier();
    shared[team_rank] = result;

    loop_boundaries.thread.team_barrier();

    // reduce across threads to thread 0
    if (team_rank == 0) {
      for (int i = 1; i < loop_boundaries.thread.team_size(); i++) {
        join(shared[0], shared[i]);
      }
    }

    loop_boundaries.thread.team_barrier();

    // broadcast result
    initialized_result = shared[0];
  }
  else {
    initialized_result = result ;
  }
}

// placeholder for future function
template< typename iType, class Lambda, typename ValueType >
KOKKOS_INLINE_FUNCTION
void parallel_reduce
  (const Impl::ThreadVectorRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries,
   const Lambda & lambda,
   ValueType& initialized_result)
{
}

// placeholder for future function
template< typename iType, class Lambda, typename ValueType, class JoinType >
KOKKOS_INLINE_FUNCTION
void parallel_reduce
  (const Impl::ThreadVectorRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries,
   const Lambda & lambda,
   const JoinType & join,
   ValueType& initialized_result)
{
}

template< typename ValueType, typename iType, class Lambda >
KOKKOS_INLINE_FUNCTION
void parallel_scan
  (const Impl::TeamThreadRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries,
   const Lambda & lambda)
{
  ValueType accum = 0 ;
  ValueType val, local_total;
  ValueType *shared = (ValueType*) loop_boundaries.thread.team_shared();
  int team_size = loop_boundaries.thread.team_size();
  int team_rank = loop_boundaries.thread.team_rank(); // member num within the team

  // Intra-member scan
  for( iType i = loop_boundaries.start; i < loop_boundaries.end; i+=loop_boundaries.increment) {
    local_total = 0;
    lambda(i,local_total,false);
    val = accum;
    lambda(i,val,true);
    accum += local_total;
  }

  shared[team_rank] = accum;
  loop_boundaries.thread.team_barrier();

  // Member 0 do scan on accumulated totals
  if (team_rank == 0) {
    for( iType i = 1; i < team_size; i+=1) {
      shared[i] += shared[i-1];
    }
    accum = 0; // Member 0 set accum to 0 in preparation for inter-member scan
  }

  loop_boundaries.thread.team_barrier();

  // Inter-member scan adding in accumulated totals
  if (team_rank != 0) { accum = shared[team_rank-1]; }
  for( iType i = loop_boundaries.start; i < loop_boundaries.end; i+=loop_boundaries.increment) {
    local_total = 0;
    lambda(i,local_total,false);
    val = accum;
    lambda(i,val,true);
    accum += local_total;
  }
}

// placeholder for future function
template< typename iType, class Lambda, typename ValueType >
KOKKOS_INLINE_FUNCTION
void parallel_scan
  (const Impl::ThreadVectorRangeBoundariesStruct<iType,Impl::TaskExec< Kokkos::Experimental::OpenMPTarget > >& loop_boundaries,
   const Lambda & lambda)
{
}


} /* namespace Kokkos */

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

#endif /* #if defined( KOKKOS_ENABLE_TASKPOLICY ) */
#endif /* #ifndef KOKKOS_IMPL_OPENMP_TASK_HPP */

