still Schur complement
Kathrin Burckhardt
tribur at vision.ee.ethz.ch
Mon Mar 17 16:54:27 CDT 2008
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?
>>
>>
>>
>
>
>
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