libtrilinos-tpetra-dev 12.4.2-2 / usr / include / trilinos / TbbTsqr_FillWithZerosTask.hpp

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#ifndef __TSQR_TBB_FillWithZerosTask_hpp
#define __TSQR_TBB_FillWithZerosTask_hpp

#include <tbb/task.h>
#include <TbbTsqr_Partitioner.hpp>
#include <Tsqr_SequentialTsqr.hpp>

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

namespace TSQR {
  namespace TBB {

    /// \class FillWithZerosTask
    /// \brief TBB task for recursive TSQR "fill with zeros" phase.
    ///
    template<class LocalOrdinal, class Scalar>
    class FillWithZerosTask : public tbb::task {
    public:
      typedef MatView<LocalOrdinal, Scalar> mat_view_type;

    private:
      typedef std::pair<mat_view_type, mat_view_type> split_type;

    public:
      FillWithZerosTask (const size_t P_first,
                         const size_t P_last,
                         mat_view_type C,
                         const SequentialTsqr<LocalOrdinal, Scalar>& seq,
                         const bool contiguous_cache_blocks = false)
        : P_first_ (P_first),
          P_last_ (P_last),
          C_ (C),
          seq_ (seq),
          contiguous_cache_blocks_ (contiguous_cache_blocks)
      {}

      tbb::task* execute ()
      {
        if (P_first_ > P_last_ || C_.empty())
          return NULL;
        else if (P_first_ == P_last_)
          {
            execute_base_case ();
            return NULL;
          }
        else
          {
            // Recurse on two intervals: [P_first, P_mid] and
            // [P_mid+1, P_last].
            const size_t P_mid = (P_first_ + P_last_) / 2;
            split_type C_split =
              partitioner_.split (C_, P_first_, P_mid, P_last_,
                                  contiguous_cache_blocks_);
            // The partitioner may decide that the current block C_
            // has too few rows to be worth splitting.  In that case,
            // C_split.second (the bottom block) will be empty.  We
            // can deal with this by treating it as the base case.
            if (C_split.second.empty() || C_split.second.nrows() == 0)
              {
                execute_base_case ();
                return NULL;
              }

            // "c": continuation task
            tbb::empty_task& c =
              *new( allocate_continuation() ) tbb::empty_task;
            // Recurse on the split
            FillWithZerosTask& topTask = *new( c.allocate_child() )
              FillWithZerosTask (P_first_, P_mid, C_split.first, seq_,
                                 contiguous_cache_blocks_);
            FillWithZerosTask& botTask = *new( c.allocate_child() )
              FillWithZerosTask (P_mid+1, P_last_, C_split.second, seq_,
                                 contiguous_cache_blocks_);
            // Set reference count of parent (in this case, the
            // continuation task) to 2 (since 2 children -- no
            // additional task since no waiting).
            c.set_ref_count (2);
            c.spawn (botTask);
            return &topTask; // scheduler bypass optimization
          }
      }

    private:
      size_t P_first_, P_last_;
      mat_view_type C_;
      SequentialTsqr<LocalOrdinal, Scalar> seq_;
      Partitioner<LocalOrdinal, Scalar> partitioner_;
      bool contiguous_cache_blocks_;

      void
      execute_base_case ()
      {
        // Fill my partition with zeros.
        seq_.fill_with_zeros (C_.nrows(), C_.ncols(), C_.get(),
                              C_.lda(), contiguous_cache_blocks_);
      }
    };
  } // namespace TBB
} // namespace TSQR


#endif // __TSQR_TBB_FillWithZerosTask_hpp