TsqrRandomizer_Epetra_MultiVector.hpp

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#ifndef __TSQR_Trilinos_Randomizer_Epetra_MultiVector_hpp
#define __TSQR_Trilinos_Randomizer_Epetra_MultiVector_hpp


#include "TsqrTypeAdaptor_Epetra_Multivector.hpp"
#include "TsqrCommFactory_Epetra.hpp"
#include "Teuchos_ArrayView.hpp"
#include <limits>
#include <stdexcept>
#include <sstream>


namespace TSQR {
  namespace Trilinos {

    template< class Gen >
    class EpetraRandomizer :
      public Randomizer< double, int, int, Epetra_MultiVector, Gen >
    {
    public:
      // The C++ compiler needs help inheriting typedefs, when both
      // the base class and the derived class are templated.
      typedef Randomizer< double, int, int, Epetra_MultiVector, Gen > base_type;
      typedef typename base_type::multivector_type multivector_type;
      typedef typename base_type::local_ordinal_type local_ordinal_type;
      typedef typename base_type::scalar_type scalar_type;

      typedef typename base_type::normalgen_ptr normalgen_ptr;
      typedef typename base_type::ordinal_messenger_ptr ordinal_messenger_ptr;
      typedef typename base_type::scalar_messenger_ptr scalar_messenger_ptr;

      EpetraRandomizer (const multivector_type& mv,
      const normalgen_ptr& pGen)
      {
  init (mv, pGen);
      }

    private:
      // mfh 14 Jul 2010: For who knows what reason, this refuses to
      // compile if you replace "double" with "scalar_type".  And no,
      // adding "typename" doesn't work either.
      typedef Teuchos::ArrayView< double >::size_type size_type;

      virtual void
      fetchDims (const multivector_type& A,
     local_ordinal_type& nrowsLocal,
     local_ordinal_type& ncols,
     local_ordinal_type& LDA) const
      {
  nrowsLocal = A.MyLength();
  ncols = A.NumVectors();
  if (nrowsLocal < ncols)
    {
      std::ostringstream os;
      os << "TSQR: The local component of the input matrix has fewer row"
        "s (" << nrowsLocal << ") than columns (" << ncols << ").  TSQR "
        "does not support this case.";
      throw std::runtime_error (os.str());
    }
  if (! A.ConstantStride())
    {
      std::ostringstream os;
      os << "TSQR does not support Epetra_MultiVector inputs that do not"
        " have constant stride.";
      throw std::runtime_error (os.str());
    }
  LDA = A.Stride();
      }

      size_type
      fetchArrayLength (const multivector_type& A) const
      {
  //typedef Teuchos::ArrayView< scalar_type >::size_type size_type;

  // Compute length (nelts) of the A.Values() array.  This only
  // makes sense if A has constant stride.  We convert from int
  // (the local_ordinal_type) to size_type, hoping that the
  // latter is no smaller than local_ordinal_type.  This gives
  // us a better chance that LDA*ncols fits in a size_type.  We
  // check for overflow both when converting each of LDA and
  // ncols from local_ordinal_type to size_type, and when
  // computing LDA*ncols (in size_type arithmetic).

  // Fetch dimensions of local part of A, as local_ordinal_type.
  local_ordinal_type nrowsLocal_LO, ncols_LO, LDA_LO;
  fetchDims (A, nrowsLocal_LO, ncols_LO, LDA_LO);

  // Convert dimensions from local_ordinal_type to size_type,
  // ensuring that the conversions don't overflow.
  const size_type LDA = static_cast< size_type > (LDA_LO);
  if (static_cast< local_ordinal_type > (LDA) != LDA_LO)
    throw std::runtime_error ("TSQR::Trilinos::EpetraRandomizer: "
            "Leading dimension of local part of "
            "Epetra_MultiVector overflowed on co"
            "nversion from local_ordinal_type to"
            " ArrayView::size_type");
  const size_type ncols = static_cast< size_type > (ncols_LO);
  if (static_cast< local_ordinal_type > (ncols) != ncols_LO)
    throw std::runtime_error ("TSQR::Trilinos::EpetraRandomizer: "
            "Number of columns of the given "
            "Epetra_MultiVector overflowed on co"
            "nversion from local_ordinal_type to"
            " ArrayView::size_type");
  // Make sure that the length of A.Values(), which is the
  // product of the leading dimension and the number of columns
  // of A, fits in a size_type.
  const size_type nelts = LDA * ncols;
  if (nelts / LDA != ncols)
    throw std::runtime_error ("TSQR::Trilinos::EpetraRandomizer: "
            " Length of A.Values() does not fit "
            "in an ArrayView::size_type");
  return nelts;
      }

      virtual Teuchos::ArrayRCP< scalar_type > 
      fetchNonConstView (multivector_type& A) const
      {
  using Teuchos::arcpFromArrayView;
  using Teuchos::arrayView;

  const size_type nelts = fetchArrayLength (A);
  // The returned ArrayRCP does NOT own A.Values().
  return arcpFromArrayView (arrayView (A.Values(), nelts));
      }

      virtual void
      fetchMessengers (const multivector_type& mv,
           scalar_messenger_ptr& pScalarMessenger,
           ordinal_messenger_ptr& pOrdinalMessenger) const
      {
  typedef EpetraCommFactory comm_factory_type;
  // mv.Comm() returns a "const Epetra_Comm&".  rcpFromRef()
  // makes a non-owning (weak) RCP out of it.  This requires
  // that the mv's Epetra_Comm object not fall out of scope,
  // which it shouldn't as long as we are computing with
  // multivectors distributed according to that communicator.
  comm_ptr pComm = Teuchos::rcpFromRef (mv.Comm());
  comm_factory_type factory;
  factory.makeMessengers (pComm, pScalarMessenger, pOrdinalMessenger);
      }
    };

  } // namespace Trilinos
} // namespace TSQR

#endif // __TSQR_Trilinos_Randomizer_Epetra_MultiVector_hpp