lapack-wrapper-getrf.cc (flens/examples/lapack-wrapper-getrf.cc)

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#include <cxxstd/iostream.h>

///

///  With header __flens.cxx__ all of FLENS gets included.

///

///  :links:  __flens.cxx__ -> file:flens/flens.cxx

#include <flens/flens.cxx>

using namespace std;

using namespace flens;

typedef double   T;

namespace flens { namespace mylapack {

template <typename MA, typename VPIV>

typename RestrictTo<IsGeMatrix<MA>::value

                 && IsIntegerDenseVector<VPIV>::value,

         typename RemoveRef<MA>::Type::IndexType>::Type

trf(MA &&A, VPIV &&piv)

{

//

//  Remove references from rvalue types

//

    typedef typename RemoveRef<MA>::Type    MatrixA;

    typedef typename MatrixA::IndexType     IndexType;

    typedef typename RemoveRef<VPIV>::Type  VectorPiv;

//

//  Create views of the arguments

//

    typename MatrixA::View    A_      = A;

    typename VectorPiv::View  piv_    = piv;

//

//  Make the views one-based

//

    A_.changeIndexBase(1,1);

    piv_.changeIndexBase(1);

    IndexType info = lapack::trf(A_, piv_);

    const IndexType diff = piv.firstIndex() - piv_.firstIndex();

    for (IndexType i=1; i<=piv_.length(); ++i) {

        piv_(i) += diff;

    }

    return info;

}

} } // namespace mylapack, flens

int

main()

{

    ///

    ///  Define some convenient typedefs for the matrix type

    ///  of our system of linear equations.

    ///

    typedef GeMatrix<FullStorage<T> >           Matrix;

    ///

    ///  We also need an extra vector type for the pivots.  The type of the

    ///  pivots is taken for the system matrix.

    ///

    typedef Matrix::IndexType                   IndexType;

    typedef DenseVector<Array<IndexType> >      IndexVector;

    ///

    ///  Set up the baby problem ...

    ///

    const IndexType m = 4,

                    n = 5;

    ///

    /// Zero based matrix and vector

    ///

    Matrix            Ab(m, n, 0, 0);

    IndexVector       piv(m, 0);

    Ab =  2,   3,  -1,   0,  20,

         -6,  -5,   0,   2, -33,

          2,  -5,   6,  -6, -43,

          4,   6,   2,  -3,  49;

    cout << "Ab = " << Ab << endl;

    ///

    /// Compute the $LU$ factorization with __lapack::trf__

    ///

    mylapack::trf(Ab, piv);

    cout << "Ab.firstRow() = " << Ab.firstRow() << endl;

    cout << "Ab.firstCol() = " << Ab.firstCol() << endl;

    cout << "Ab = " << Ab << endl;

    cout << "piv = " << piv << endl;

}