TbbTsqr_RevealRankTask.hpp

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//                 Anasazi: Block Eigensolvers Package
//                 Copyright (2010) Sandia Corporation
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// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
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#ifndef __TSQR_TBB_RevealRankTask_hpp
#define __TSQR_TBB_RevealRankTask_hpp

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


namespace TSQR {
  namespace TBB {
    
    template< class LocalOrdinal, class Scalar >
    class RevealRankTask : public tbb::task {
    public:
      typedef MatView< LocalOrdinal, Scalar > mat_view;
      typedef ConstMatView< LocalOrdinal, Scalar > const_mat_view;
      typedef std::pair< mat_view, mat_view > split_type;
      typedef SequentialTsqr< LocalOrdinal, Scalar > seq_tsqr_type;

      RevealRankTask (const size_t P_first, 
          const size_t P_last,
          const mat_view& Q,
          const const_mat_view& U,
          const seq_tsqr_type& seq,
          const bool contiguous_cache_blocks) :
  P_first_ (P_first), 
  P_last_ (P_last), 
  Q_ (Q),
  U_ (U),
  seq_ (seq),
  contiguous_cache_blocks_ (contiguous_cache_blocks)
      {}

      tbb::task* execute () {
  using tbb::task;

  if (P_first_ > P_last_ || Q_.empty())
    return NULL; // shouldn't get here, but just in case...
  else if (P_first_ == P_last_)
    {
      // Use SequentialTsqr to compute Q*U for this core's local
      // part of Q.  The method is called "Q_times_B" so that it
      // doesn't suggest any orthogonality of the B input
      // matrix, though in this case B is U and U is orthogonal.
      seq_.Q_times_B (Q_.nrows(), Q_.ncols(), Q_.get(), Q_.lda(),
          U_.get(), U_.lda(), contiguous_cache_blocks_);
      return NULL;
    }
  else
    {
      // "c": continuation task
      tbb::empty_task& c = *new( allocate_continuation() ) tbb::empty_task;

      // 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 out_split = 
        partitioner_.split (Q_, P_first_, P_mid, P_last_, 
          contiguous_cache_blocks_);

      RevealRankTask& topTask = *new( c.allocate_child() )
        RevealRankTask (P_first_, P_mid, out_split.first, seq_, 
            contiguous_cache_blocks_);
      RevealRankTask& botTask = *new( c.allocate_child() )
        RevealRankTask (P_mid+1, P_last_, out_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 Q_;
      const_mat_view U_;
      SequentialTsqr< LocalOrdinal, Scalar > seq_;
      Partitioner< LocalOrdinal, Scalar > partitioner_;
      bool contiguous_cache_blocks_;
    };

  } // namespace TBB
} // namespace TSQR


#endif // __TSQR_TBB_RevealRankTask_hpp