getfem-users
[Top][All Lists]

## Re: [Getfem-users] Assembly of rectangular matrix: order of trial and te

 From: Yves Renard Subject: Re: [Getfem-users] Assembly of rectangular matrix: order of trial and test FE spaces Date: Sun, 8 Nov 2015 18:52:31 +0100 (CET)

Dear Domenico,

You can of course obtain the transposed matrix. In fact just by interverting
the terms in the assembly string:

generic_assembly assem("M$1(#1,#2)+=comp(Base(#2).vGrad(#1))(:,:,i,i);"); assem.push_mi(mim); assem.push_mf(mf_u); assem.push_mf(mf_p); assem.push_mat(M); assem.assembly(rg); Yves. ----- Mail original ----- De: "Domenico Notaro" <address@hidden> À: "yves renard" <address@hidden> Cc: "getfem-users" <address@hidden> Envoyé: Dimanche 8 Novembre 2015 18:08:54 Objet: Re: [Getfem-users] Assembly of rectangular matrix: order of trial and test FE spaces Dear Professor Renard, thank you for your prompt reply. Actually, the solution you suggest me was exactly my first attempt (a), apart from a stupid typing error (obviously it was "vBase().Normal()"-->"vGrad()"!). But this assembly routine returns a mf_u.nb_dof() x mf_p.nb_dof() matrix while I need the transposed... That's why I arrived to option (b), since I thought the dimensions of output matrix follow from the order of mesh_fem pushes. Finally, if I have understood you correctly, in the main file I have to: - define a blank transposed matrix: sparse_matrix_type D(mf_u.nb_dof(), mf_p.nb_dof()); - call the assembly routine (a) over this matrix D - use gmm::transposed(D) every time I need the matrix D=\int DIV(u).q And I am supposed to do the same for every rectangular matrix assembly? Best regards, Domenico ________________________________________ Da: Yves Renard <address@hidden> Inviato: domenica 8 novembre 2015 17.19 A: Domenico Notaro Cc: getfem-users Oggetto: Re: [Getfem-users] Assembly of rectangular matrix: order of trial and test FE spaces Dear Domenico, The assembly in the low-level generic assembly should be generic_assembly assem("M$1(#1,#2)+=comp(vGrad(#1).Base(#2))(:,i,i,:);");
assem.push_mi(mim);
assem.push_mf(mf_u);
assem.push_mf(mf_p);
assem.push_mat(M);
assem.assembly(rg);

(You have it in getfem_assembling.h for instance at lines 769 (asm_stokes_B).

Note that you can obtain this also with the high-level generic assembly with an
assembly string of the form "Div_Test_u*Test_p".

Yves.

----- Mail original -----
Envoyé: Samedi 7 Novembre 2015 12:45:32
Objet: [Getfem-users] Assembly of rectangular matrix: order of trial and
test FE spaces

Dear GetFEM users,

I would like to have a double-check on a very basic issue, that is the order of
trial and test spaces in rectangular matrix assembly.

In particular, which of the following assembly routines returns the matrix

$M = \int DIV(u).q$

where u is the trial mf_u function and q is the test mf_p function?

(a)

generic_assembly
assem("M$1(#1,#2)+=comp(vBase(#1).Normal().Base(#2))(:,i,i,:);"); assem.push_mi(mim); assem.push_mf(mf_u); assem.push_mf(mf_p); assem.push_mat(M); assem.assembly(rg); (b) generic_assembly assem("M$1(#2,#1)+=comp(vBase(#2).Normal().Base(#1))(:,i,i,:);");
assem.push_mi(mim);
assem.push_mf(mf_p);

assem.push_mf(mf_u);
assem.push_mat(M);
assem.assembly(rg);

(c)

generic_assembly
assem("M\$1(#1,#2)+=comp(Base(#1).vBase(#2).Normal())(:,:,i,i);");
assem.push_mi(mim);
assem.push_mf(mf_p);

assem.push_mf(mf_u);
assem.push_mat(M);
assem.assembly(rg);

I want to build a matrix M with mf_p.nb_dof() rows and mf_u.nb_dof() columns
(i.e. in the main file I have " sparse_matrix_type M(mf_p.nb_dof(),
mf_u.nb_dof()); ")

Domenico

_______________________________________________
Getfem-users mailing list