tut08-page01-example5.cc (flens/examples/tut08-page01-example5.cc)

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#include <cxxstd/iostream.h>

#include <flens/flens.cxx>

using namespace std;

using namespace flens;

typedef double   T;

int

main()

{

    typedef TpMatrix<PackedStorage<T, Upper> >  Matrix;

    typedef DenseVector<Array<T> >              Vector;

    typedef Matrix::IndexType                   IndexType;

    typedef DenseVector<Array<IndexType> >      IndexVector;

    const IndexType n = 4;

    ///

    /// The parameter define the dimensions (always a square matrix)

    ///

    Matrix         Ap(n);

    Vector         b(n), x(n);

    IndexVector    piv(n);

    for (IndexType i = 1; i <= n; ++i)

        for (IndexType j = i; j <= n; ++j)

            Ap(i,j) = i + 2*j;

    b = 20,

       -33,

       -43,

        49;

    cout << "Ap = " << Ap.symmetric() << endl;

    cout << "b  = " << b << endl;

    ///

    /// Compute $x = 0.5*(Ap+Ap^T) b$

    ///

    x = Ap.symmetric()*b;

    cout << "x = " << x << endl;

    ///

    /// Solve $x = 0.5*(Ap+Ap^T) b$

    ///

    lapack::sv(Ap.symmetric(), piv, x);

    cout << "b = " << b << endl;

    return 0;

}