Teuchos_SerialDenseHelpers.hpp

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#ifndef _TEUCHOS_SERIALDENSEHELPERS_HPP_
#define _TEUCHOS_SERIALDENSEHELPERS_HPP_

#include "Teuchos_ScalarTraits.hpp"
#include "Teuchos_DataAccess.hpp"
#include "Teuchos_ConfigDefs.hpp"
#include "Teuchos_Assert.hpp"
#include "Teuchos_SerialDenseMatrix.hpp"  
#include "Teuchos_SerialSymDenseMatrix.hpp" 
#include "Teuchos_SerialDenseVector.hpp"  

namespace Teuchos {

template<typename OrdinalType, typename ScalarType>
void symMatTripleProduct( ETransp transw, const ScalarType alpha, const SerialSymDenseMatrix<OrdinalType, ScalarType>& A, 
        const SerialDenseMatrix<OrdinalType, ScalarType>& W, SerialSymDenseMatrix<OrdinalType, ScalarType>& B )
{
  // Local variables.
  // Note: dimemensions of W are obtained so we can compute W^T*A*W for either cases.
  OrdinalType A_nrowcols = A.numRows();  // A is a symmetric matrix and is assumed square. 
  OrdinalType B_nrowcols = (ETranspChar[transw]!='N') ? W.numCols() : W.numRows();
  OrdinalType W_nrows = (ETranspChar[transw]!='N') ? W.numRows() : W.numCols();
  OrdinalType W_ncols = (ETranspChar[transw]!='N') ? W.numCols() : W.numRows();
  
  bool isBUpper = B.upper();

  // Check for consistent dimensions.
  TEUCHOS_TEST_FOR_EXCEPTION( B_nrowcols != B.numRows(), std::out_of_range,
    "Teuchos::symMatTripleProduct<>() : "
    "Num Rows/Cols B (" << B.numRows() << ") inconsistent with W ("<< B_nrowcols << ")");
  TEUCHOS_TEST_FOR_EXCEPTION( A_nrowcols != W_nrows, std::out_of_range,
    "Teuchos::symMatTripleProduct<>() : "
    "Num Rows/Cols A (" << A_nrowcols << ") inconsistent with W ("<< W_nrows << ")");

  // Scale by zero, initialized B to zeros and return.
  if ( alpha == ScalarTraits<ScalarType>::zero() )
  {
    B.putScalar();
    return;
  }

  // Workspace.
  SerialDenseMatrix<OrdinalType, ScalarType> AW;

  // BLAS class.
  BLAS<OrdinalType, ScalarType> blas;
  ScalarType one = Teuchos::ScalarTraits<ScalarType>::one();
  ScalarType zero = Teuchos::ScalarTraits<ScalarType>::zero();

  // Separate two cases because BLAS only supports symmetric matrix-matrix multply w/o transposes.
  if (ETranspChar[transw]!='N') {
    // Size AW to compute A*W
    AW.shapeUninitialized(A_nrowcols,W_ncols);
  
    // A*W
    AW.multiply( Teuchos::LEFT_SIDE, alpha, A, W, ScalarTraits<ScalarType>::zero() );
    
    // B = W^T*A*W
    if (isBUpper) {
      for (int j=0; j<B_nrowcols; ++j)
  blas.GEMV( transw, W_nrows, j+1, one, W.values(), W.stride(), AW[j], 1, zero, &B(0,j), 1 );
    }
    else {
      for (int j=0; j<B_nrowcols; ++j)
  blas.GEMV( transw, W_nrows, B_nrowcols-j, one, W[j], W.stride(), AW[j], 1, zero, &B(j,j), 1 );
    }
  }
  else {
    // Size AW to compute W*A
    AW.shapeUninitialized(W_ncols, A_nrowcols);

    // W*A
    AW.multiply( Teuchos::RIGHT_SIDE, alpha, A, W, ScalarTraits<ScalarType>::zero() );

    // B = W*A*W^T
    if (isBUpper) {
      for (int j=0; j<B_nrowcols; ++j)
  for (int i=0; i<=j; ++i) 
    blas.GEMV( transw, 1, A_nrowcols, one, &AW(i,0), AW.stride(), &W(j,0), W.stride(), zero, &B(i,j), 1 );
    }
    else {
      for (int j=0; j<B_nrowcols; ++j)
  for (int i=j; i<B_nrowcols; ++i) 
    blas.GEMV( transw, 1, A_nrowcols, one, &AW(i,0), AW.stride(), &W(j,0), W.stride(), zero, &B(i,j), 1 );
    }
  }

  return;
}
  
template<typename OrdinalType, typename ScalarType>
SerialDenseVector<OrdinalType,ScalarType>
getCol( DataAccess CV, SerialDenseMatrix<OrdinalType, ScalarType>& A, const OrdinalType col )
{
  return SerialDenseVector<OrdinalType, ScalarType>(CV, A[col], A.numRows());
}

template<typename OrdinalType, typename ScalarType>
bool setCol( const SerialDenseVector<OrdinalType, ScalarType>& v,
             const OrdinalType col,
             SerialDenseMatrix<OrdinalType, ScalarType>& A )
{
  if (v.length() != A.numRows()) return false;

  std::copy(v.values(),v.values()+v.length(),A[col]);

  return true;
}

} // namespace Teuchos

#endif /* _TEUCHOS_SERIALDENSEHELPERS_HPP_ */