still Schur complement

[Lisandro Dalcin]

OK,

Have you considered using MATSHELL for this ??

On 3/17/08, Kathrin Burckhardt <tribur at vision.ee.ethz.ch> wrote:
> Dear Lisandro,
>
>
>  > I'm not completelly sure what are you actually trying to do. It seems
>  > you know how to actually compute the local Schur complement in a
>  > entry-by-entry basis. In that case, your way is semms to be OK.
>
>
> What do you mean with entry-by-entry basis? Anyway, I have the local
>  Schur complement explicitely, in form of a matrix (or C++ vector).
>
>
>
>  > However, you get a error because of a inner implementation detail of
>  > MATIS.  Do de following: set the local-to-global mapping AFTER setting
>  > the matrix type. This way, your code should now work.
>
>
> Unfortunately, changing the order of the Mat-commands gives me the same
>  error. I guess I found the origin of the problem:
>
>  I put it in the order below because I thought to avoid
>
>  [2]PETSC ERROR: Sum of local lengths 3916 does not equal global length 1958
>
>  which is due to the fact that in the case of 2 Subdomains and 2
>  processors, e.g., it is NPb=NPb_tot in the Schur system, instead of
>  NPb=NPb_tot/2. However, I realize just now that the order of the
>  Mat-commands has no influence on this, and that the error mentioned
>  below has probably its origin there.
>
>  I have chosen MATIS because in the manual page of MatCreateIS() it is
>  written "...m and n are NOT related to the size of the map", but maybe I
>  understand this setence wrong? How can I choose m,n and M,N
>  independently?
>
>
>
>
>  > On 3/17/08, Kathrin Burckhardt <tribur at vision.ee.ethz.ch> wrote:
>  >> Dear all,
>  >>
>  >>  My problem, once again and more concrete:
>  >>
>  >>  I have given the local Schur matrices Si and I would like to set-up the
>  >>  global matrix S without assembling the Si on one processor.
>  >>
>  >>  I thought "MATIS" is the suitable matrix type, but I don't succeed in
>  >>  using it. My code is:
>  >>
>  >>      IS is;
>  >>      ISCreateGeneral(PETSC_COMM_SELF, NPb, &uBId_global[0], &is);
>  >>      ISLocalToGlobalMapping mapping;
>  >>      ISLocalToGlobalMappingCreateIS(is, &mapping);
>  >>      Mat Stot;
>  >>      MatCreate(PETSC_COMM_WORLD,&Stot);
>  >>      MatSetLocalToGlobalMapping(Stot, mapping);
>  >>      MatSetSizes(Stot,NPb,NPb,NPb_tot,NPb_tot);
>  >>      MatSetType(Stot,MATIS);
>  >>     //or, alternatively
>  >>     //MatCreateIS(PETSC_COMM_WORLD,NPb,NPb,NPb_tot,NPb_tot,mapping,&Stot);
>  >>      for(int i=0; i<NPb; i++)
>  >>        for(int j=0; j<NPb; j++)
>  >>         MatSetValuesLocal(Stot, 1, &i, 1, &j, &S(i+1,j+1), ADD_VALUES);
>  >>
>  >>  And I got the error
>  >>
>  >>  [1]PETSC ERROR: MatSetValuesLocal() line 1471 in
>  >>  src/mat/interface/matrix.c
>  >>  [1]PETSC ERROR: --------------------- Error Message
>  >>  ------------------------------------
>  >>  [1]PETSC ERROR: Object is in wrong state!
>  >>  [1]PETSC ERROR: Object Type not set: Argument # 1!
>  >>
>  >>  Can you tell me what's wrong?
>  >>
>  >>
>  >>
>  >
>  >
>  >
>
>


-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
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