Re: [Getfem-users] Question on Preconditioners

[Bwalya Malama]

>
> The diagonal precondtioner just stores the inverse (if nonzero)  of the
> diagonal of the matrix argument of the constructor. All matrix types are
> allowed. But off course, the preconditioner has to be built only when the
> the
> matrix is filled. If you need to declare the preconditioner before you
> fill
> the matrix, you can declare it without argument, then use P.build_with(SM)
> to
> build the preconditioner. For instance:
>
> typedef gmm::row_matrix< gmm::wsvector<complex<double> > > mymatrixtype;
> mymatrixtype C(N2,N2);
> gmm::diagonal_precond<mymatrixtype>  P();
>
> // ...
> ... fill C
> // ...
>
> P.build_with(C);
>
> Sincerly,
>
> Yves.
>
>
>
> Le Jeudi 5 Octobre 2006 17:47, vous avez écrit :
>> I have an embarassingly simple question. In the user manual for gmm++
>> there is the following:
>>
>> >>>>> gmm::diagonal_precond<matrix_type> P(SM)
>>
>> The question is what is SM? Is this the coefficient matrix from which
>> the
>> diagonal is extracted? If my coefficient matrix is of type:
>>
>> >>>>> gmm::row_matrix< gmm::wsvector<complex<double> > >
>>
>> what matrix type should matrices P and SM be?
>
>
>
>
>> Hi:
>>
>> I am trying to solve a system of equations using iterative solver, QMR,
>> in
>> particular. I have a problem with getting preconditioners. I tried the
>> following, where C(N2,N2) is the coefficient matrix:
>>
>> **********************
>> gmm::row_matrix< gmm::wsvector<complex<double> > > C(N2,N2);
>> gmm::row_matrix<std::vector<std::complex<double> > > C1(N2,N2);
>> gmm::copy(C,C1);
>> gmm::diagonal_precond<gmm::row_matrix<std::vector<std::complex<double> >
>> > >
>> P(C1);
>>
>> ****************
>>
>> This did not work owing to the large size of C1(N2,N2). What is
>> permissible for matrix_type in "gmm::diagonal_precond<matrix_type>? Note
>> that the I tried the following and it did not work:
>>
>> gmm::diagonal_precond<gmm::row_matrix<std::vector<std::complex<double> >
>> >
>>
>> > P(C);
>>
>> Please help. It appears that matrix_type cannot be:
>> gmm::row_matrix< gmm::wsvector<complex<double> > >
>>
>> Sincerely,
>> -- Bwalya
>> Bwalya Malama, Ph.D.
>> Center for Geophysical Research of the Shallow Subsurface
>> Boise State University
>> Boise, Idaho
>> tel: 208-426-2959
>> email: address@hidden
>>
>> _______________________________________________
>> Getfem-users mailing list
>> address@hidden
>> https://mail.gna.org/listinfo/getfem-users
>
> --
> -------------------------------------------------------------------------
>   Yves Renard (address@hidden)       tel : (33) 04.72.43.80.11
>   Pole de Mathematiques, INSA de Lyon          fax : (33) 04.72.43.85.29
>   Departement d'Informatique
>   Institut Camille Jordan - UMR 5208
>   20, rue Albert Einstein
>   69621 Villeurbanne Cedex, FRANCE
>   http://math.univ-lyon1.fr/~renard
> -------------------------------------------------------------------------
>
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>


-- 
Bwalya Malama, Ph.D.
Center for Geophysical Research of the Shallow Subsurface
Boise State University
Boise, Idaho
tel: 208-426-2959
email: address@hidden