transv.h

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/*

*
* Template Numerical Toolkit (TNT): Linear Algebra Module
*
* Mathematical and Computational Sciences Division
* National Institute of Technology,
* Gaithersburg, MD USA
*
*
* This software was developed at the National Institute of Standards and
* Technology (NIST) by employees of the Federal Government in the course
* of their official duties. Pursuant to title 17 Section 105 of the
* United States Code, this software is not subject to copyright protection
* and is in the public domain.  The Template Numerical Toolkit (TNT) is
* an experimental system.  NIST assumes no responsibility whatsoever for
* its use by other parties, and makes no guarantees, expressed or implied,
* about its quality, reliability, or any other characteristic.
*
* BETA VERSION INCOMPLETE AND SUBJECT TO CHANGE
* see http://math.nist.gov/tnt for latest updates.
*
*/



// Matrix Transpose Views

#ifndef TRANSV_H
#define TRANSV_H

#include <iostream>
#include <cassert>
#include "vec.h"

namespace TNT
{

template <class Array2D>
class Transpose_View
{
    protected:

        const Array2D &  A_;

    public:

        typedef typename Array2D::element_type T;
        typedef         T   value_type;
        typedef         T   element_type;
        typedef         T*  pointer;
        typedef         T*  iterator;
        typedef         T&  reference;
        typedef const   T*  const_iterator;
        typedef const   T&  const_reference;


        const Array2D & array()  const { return A_; }
        Subscript num_rows() const { return A_.num_cols();}
        Subscript num_cols() const { return A_.num_rows();}
        Subscript lbound() const { return A_.lbound(); }
        Subscript dim(Subscript i) const
        {
#ifdef TNT_BOUNDS_CHECK
            assert( A_.lbound() <= i);
            assert( i<= A_.lbound()+1);
#endif
            if (i== A_.lbound())
                return num_rows();
            else
                return num_cols();
        }


        Transpose_View(const Transpose_View<Array2D> &A) : A_(A.A_) {};
        Transpose_View(const Array2D &A) : A_(A) {};


        inline const typename Array2D::element_type & operator()(
            Subscript i, Subscript j) const
        {
#ifdef TNT_BOUNDS_CHECK
        assert(lbound()<=i);
        assert(i<=A_.num_cols() + lbound() - 1);
        assert(lbound()<=j);
        assert(j<=A_.num_rows() + lbound() - 1);
#endif

            return A_(j,i);
        }


};

template <class Matrix>
Transpose_View<Matrix> Transpose_view(const Matrix &A)
{
    return Transpose_View<Matrix>(A);
}

template <class Matrix, class T>
Vector<T> matmult(
    const Transpose_View<Matrix> & A, 
    const Vector<T> &B)
{
    Subscript  M = A.num_rows();
    Subscript  N = A.num_cols();

    assert(B.dim() == N);

    Vector<T> x(N);

    Subscript i, j;
    T tmp = 0;

    for (i=1; i<=M; i++)
    {
        tmp = 0;
        for (j=1; j<=N; j++)
            tmp += A(i,j) * B(j);
        x(i) = tmp;
    }

    return x;
}

template <class Matrix, class T>
inline Vector<T> operator*(const Transpose_View<Matrix> & A, const Vector<T> &B)
{
    return matmult(A,B);
}


template <class Matrix>
std::ostream& operator<<(std::ostream &s, const Transpose_View<Matrix> &A)
{
    Subscript M=A.num_rows();
    Subscript N=A.num_cols();

    Subscript start = A.lbound();
    Subscript Mend = M + A.lbound() - 1;
    Subscript Nend = N + A.lbound() - 1;

    s << M << "  " << N << endl;
    for (Subscript i=start; i<=Mend; i++)
    {
        for (Subscript j=start; j<=Nend; j++)
        {
            s << A(i,j) << " ";
        }
        s << endl;
    }


    return s;
}

} // namespace TNT

#endif // TRANSV_H