[petsc-users] Convert mat SEQAIJ to MPIAIJ

[Thomas Witkowski]

     Mat seqMat;
     MatCreateSeqAIJ(PETSC_COMM_SELF, 10, 10, 0, PETSC_NULL, &seqMat);

     Mat nestMat;
     MatCreateNest(PETSC_COMM_WORLD, 1, PETSC_NULL, 1, PETSC_NULL, 
&seqMat, &nestMat);

Results in the following error message:

[0]PETSC ERROR: PetscSplitOwnership() line 93 in 
/home/thomas/software/petsc-3.3-p0/src/sys/utils/psplit.c Sum of local 
lengths 20 does not equal global length 10, my local length 10
   likely a call to VecSetSizes() or MatSetSizes() is wrong.
See http://www.mcs.anl.gov/petsc/documentation/faq.html#split
[1]PETSC ERROR: PetscSplitOwnership() line 93 in 
/home/thomas/software/petsc-3.3-p0/src/sys/utils/psplit.c Sum of local 
lengths 20 does not equal global length 10, my local length 10
   likely a call to VecSetSizes() or MatSetSizes() is wrong.


Thomas


Am 04.09.2012 17:36, schrieb Matthew Knepley:
> On Tue, Sep 4, 2012 at 10:28 AM, Thomas Witkowski 
> <thomas.witkowski at tu-dresden.de 
> <mailto:thomas.witkowski at tu-dresden.de>> wrote:
>
>     Am 04.09.2012 17:20, schrieb Matthew Knepley:
>>     On Tue, Sep 4, 2012 at 9:52 AM, Thomas Witkowski
>>     <thomas.witkowski at tu-dresden.de
>>     <mailto:thomas.witkowski at tu-dresden.de>> wrote:
>>
>>>
>>>         http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATNEST.html
>>>
>>         As I wrote in my initial question, each rank contains one and
>>         only one seqaij matrix, which all should be joined to one
>>         global matrix such that each local matrix is the
>>         corresponding diagonal block of the mpiaij matrix. I think,
>>         this does not work with nested matrices?
>>
>>
>>     Why does this not work? I really think you are making this harder
>>     than it has to be.
>>
>     Mh, maybe I have an incomplete view of the possibilities how to
>     use nested matrices.
>
>     To become more specific: In the case of two mpi tasks, each
>     containing one seqaij matrix, how to call MatCreateNest? Is this
>     correct:
>
>     Mat A;
>     MatCreaeteNest(PETSC_COMM_WORLD, 2, PETSC_NULL, 2, PETSC_NULL, V ,&A);
>
>      ^^^ This should be 1.
>
>    Matt
>
>     and V is defined on rank 0 as
>
>     Mat V[2] = {seqMat, PETSC_NULL} ;
>
>     and and rank 1 as
>
>     Mat V[2] = {PETSC_NULL, seqMat};
>
>
>     Thomas
>>        Matt
>>
>>         Thomas
>>
>>>
>>>>             Hong
>>>>
>>>>>
>>>>>                 Thomas :
>>>>>
>>>>>                     In my FETI-DP code, each rank creates a SEQAIJ
>>>>>                     matrix that represents the discretization of
>>>>>                     the interior domain. Just for debugging, I
>>>>>                     would like to join these sequential matrices
>>>>>                     to one global MPIAIJ matrix. This matrix has
>>>>>                     no off diagonal nnzs and should be stored
>>>>>                     corresponding to the ranks unknowns, thus,
>>>>>                     first all rows of the first rank and so on.
>>>>>                     What's the most efficient way to do this? Is
>>>>>                     it possible to create this parallel matrix
>>>>>                     just as a view of the sequential ones, so
>>>>>                     without copying the data? Thanks for any advise.
>>>>>
>>>>>
>>>>>                 http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateMPIAIJConcatenateSeqAIJ.html
>>>>>
>>>>>                 Note: entries in seqaij matrices are copied into a
>>>>>                 mpiaij matrix without
>>>>>                 inter-processor communication. Use petsc-3.3 for
>>>>>                 this function.
>>>>
>>>>                 The function does not do what I expect. For
>>>>                 example, if we have two mpi task and each contains
>>>>                 one local square matrix with n rows, I want to
>>>>                 create a global square matrix with 2n rows. This
>>>>                 function create a non-square matrix of size 2n x n.
>>>>
>>>>                 Thomas
>>>>
>>>>
>>
>>
>>
>>     -- 
>>     What most experimenters take for granted before they begin their
>>     experiments is infinitely more interesting than any results to
>>     which their experiments lead.
>>     -- Norbert Wiener
>
>
>
>
> -- 
> What most experimenters take for granted before they begin their 
> experiments is infinitely more interesting than any results to which 
> their experiments lead.
> -- Norbert Wiener

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