Subject: Re: [ublas] novice question. how to use ublas bindings
From: Karl Meerbergen (karl.meerbergen_at_[hidden])
Date: 2009-08-21 15:06:56
Dear Luca,
If you use syev('V', 'U', matrix,...)
you do not need a symmetric_adaptor.
Best,
Karl
Luca Sbardella wrote:
> 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]
> <mailto: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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>
>
>
>
> --
> Dr Luca Sbardella
> Director
> Dynamic Quant Ltd
>
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