Re: [Getfem-users] Assembly of rectangular matrix: order of trial and test FE spaces

[Yves Renard]

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 -----
De: "Domenico Notaro" <address@hidden>
À: "getfem-users" <address@hidden>
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()); ") 










Thank you in advance, 

Domenico 

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