TbbTsqr_ExplicitQTask.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_ExplicitQTask_hpp
#define __TSQR_TBB_ExplicitQTask_hpp

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


namespace TSQR {
  namespace TBB {
    
    template< class LocalOrdinal, class Scalar >
    class ExplicitQTask : public tbb::task {
    private:
      typedef MatView< LocalOrdinal, Scalar > mat_view;
      typedef ConstMatView< LocalOrdinal, Scalar > const_mat_view;
      typedef std::pair< mat_view, mat_view > split_t;
      typedef std::pair< const_mat_view, const_mat_view > const_split_t;

    public:
      ExplicitQTask (const size_t P_first__, 
         const size_t P_last__,
         MatView< LocalOrdinal, Scalar > Q_out,
         const SequentialTsqr< LocalOrdinal, Scalar >& seq,
         const bool contiguous_cache_blocks) :
  P_first_ (P_first__), P_last_ (P_last__), Q_out_ (Q_out),
  seq_ (seq), contiguous_cache_blocks_ (contiguous_cache_blocks)
      {}

      tbb::task* execute () {
  if (P_first_ > P_last_ || Q_out_.empty())
    return NULL;
  else if (P_first_ == P_last_)
    {
      // Fill my partition with zeros.
      seq_.fill_with_zeros (Q_out_.nrows(), Q_out_.ncols(), Q_out_.get(), 
          Q_out_.lda(), contiguous_cache_blocks_);

      // If our partition is the first (topmost), fill it with
      // the first Q_out.ncols() columns of the identity matrix.
      if (P_first_ == 0)
        {
    // Fetch the topmost cache block of my partition.  Its
    // leading dimension should be set correctly by
    // top_block().
    mat_view Q_out_top = seq_.top_block (Q_out_, contiguous_cache_blocks_);
    // Set the top block of Q_out to the first ncols
    // columns of the identity matrix.
    for (LocalOrdinal j = 0; j < Q_out_top.ncols(); ++j)
      Q_out_top(j,j) = Scalar(1);
        }
      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_t Q_split = 
        partitioner_.split (Q_out_, P_first_, P_mid, P_last_,
          contiguous_cache_blocks_);

      ExplicitQTask& topTask = *new( c.allocate_child() )
        ExplicitQTask (P_first_, P_mid, Q_split.first, seq_, 
           contiguous_cache_blocks_);
      ExplicitQTask& botTask = *new( c.allocate_child() )
        ExplicitQTask (P_mid+1, P_last_, Q_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_out_;
      SequentialTsqr< LocalOrdinal, Scalar > seq_;
      Partitioner< LocalOrdinal, Scalar > partitioner_;
      bool contiguous_cache_blocks_;
    };

  } // namespace TBB
} // namespace TSQR


#endif // __TSQR_TBB_ExplicitQTask_hpp