Re: [ublas] novice question. how to use ublas bindings

Subject: Re: [ublas] novice question. how to use ublas bindings
From: Luca Sbardella (luca_at_[hidden])
Date: 2009-08-21 13:28:16

Summarising my findings:

1) The binding won't compile when using a *ublas::matrix* for a symmetric
eigenvalue problem.
2) It won't compile if I use the *ublas::symmetric*_matrix instead
(*leading_dimension
* method missing in the matrix_traits for a symmetric_matrix).
3) It does work when I use the *ublas::symmetric_adaptor* wrapper:

and this is a snippet of the client code

#include <boost/numeric/bindings/lapack/driver/syev.hpp>
#include <boost/numeric/bindings/traits/type_traits.hpp>
#include <boost/numeric/bindings/traits/ublas_symmetric.hpp>
#include <boost/numeric/bindings/traits/ublas_vector.hpp>

template<typename T>
int syevtest(int N) {
    namespace ublas  = boost::numeric::ublas;
    namespace lapack = boost::numeric::bindings::lapack;
    typedef ublas::matrix<T, ublas::column_major>        matrix_type;
    typedef ublas::vector<T>                            vector_type;

    // Set matrix
    matrix_type a(N,N);
    vector_type e1(N);

    randomize_upper(a);

    ublas::symmetric_adaptor<matrix_type,ublas::upper> sym(a);

    lapack::syev('V',sym,e1);
    return 0;
}

int test() {
    syevectors<float>(10);
    syevectors<double>(10);
    return 0;
}

Thanks for help

Luca

2009/8/21 Thomas Klimpel <Thomas.Klimpel_at_[hidden]>

> Luca Sbardella wrote:
> > I went to bindings/traits/ublas_matrix.hpp and in the struct
> matrix_detail_traits the uplo_type is not defined.
> >
> > Am I missing something?
>
> uplo_type is used to indicate which part of a symmetric or hermitian matrix
> is stored. It should be either upper_t or lower_t. The file
> matrix_traits.hpp contains the following:
>
>  // upper/lower non-unit/unit triangular type tags
>  struct upper_t {};
>  struct lower_t {};
>  struct unit_upper_t {};
>  struct unit_lower_t {};
>
> I have to admit that I'm not aware of any special triangular matrix types,
> but there are special matrix types for symmetric and hermitian matrix types.
> So it's possible that including traits/ublas_symmetric.hpp and
> traits/ublas_hermitian.hpp will solve your problem.
>
> Conclusion:
> The uplo_type is only meaningful for symmetric, hermitian or triangular
> matrix types. I believe that only symmetric and hermitian matrix types are
> directly supported by ublas, so these type tags are only used for symmetric
> and hermitian matrices. So including traits/ublas_symmetric.hpp and
> traits/ublas_hermitian.hpp in the "client" code (i.e. the test case) and
> using the corresponding symmetric/hermitian matrix classes or matrix class
> adaptors from ublas should help with this problem.
>
> Regards,
> Thomas
> _______________________________________________
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> ublas_at_[hidden]
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> Sent to: luca_at_[hidden]
>

-- 
Dr Luca Sbardella
Director
Dynamic Quant Ltd