[petsc-users] Problem with MPI, MatAXPY and SAME_NONZERO_PATTERN
Matthew Knepley
knepley at gmail.com
Fri Mar 27 10:26:36 CDT 2015
On Fri, Mar 27, 2015 at 10:16 AM, Klaus Kaiser <kaiser at igpm.rwth-aachen.de>
wrote:
> Hallo Matthew,
>
> thanks for your fast response. With "no beside the nonzero structure" I
> meant, that I do not create a different non-zero structure while I'm adding
> values to my matrices.
>
> I also tried MAT_COPY_VALUES and the result was the same.
>
Please send the small example and we will figure out what is going wrong.
Thanks,
Matt
> I do not get a error message but the resulting matrix is wrong. Here I
> have a short example. The first 9 rows and first 3 colomn of the matrices
> Ah, At and Ah+At on the first processor (of 8):
>
> Ah:
> 0: 60.3553 -0.249975
> 2.77556e-17
> 1: 0
> 60.3553 0
> 2: 0 0
> 60.3553
> 3: 17.6777 0.374962
> 0.124987
> 4: 0
> 17.6777 0
> 5: 0 0
> 17.6777
> 6: -7.32233 -0.124987
> 0.374962
> 7: 0
> -7.32233 0
> 8: 0 0
> -7.32233
>
>
> At:
> 0: 0
> 0 0
> 1: 2500
> 0 0
> 2: -4.54747e-13
> 0 0
> 3: 0
> 0 0
> 4: 1250
> 0 0
> 5: 1250
> 0 0
> 6: 0
> 0 0
> 7: 1250
> 0 0
> 8: 3750
> 0 0
>
> Ah+At
> 0: 60.3553 -0.249975
> 2.77556e-17
> 1: 2500
> 60.3553 0
> 2: -4.54747e-13 0
> 60.3553
> 3: 17.6777 0.374962
> 0.124987
> 4: 0
> 17.6777 0
> 5: 0 0
> 17.6777
> 6: -7.32233 -0.124987
> 0.374962
> 7: 0
> -7.32233 0
> 8: 0 0
> -7.32233
>
> you can see the first 3 rows of the resulting matrix looks exactly like
> what I would expect, but the last 6 rows only consists of the values of Ah.
> When you would also look on the matrix A and A+Ah+At you would also see,
> that values where both matrices have an nonzero entry are not sum correctly.
>
> Best
>
> Klaus
>
> On 03/27/2015 03:59 PM, Matthew Knepley wrote:
>
> On Fri, Mar 27, 2015 at 9:48 AM, Klaus Kaiser <kaiser at igpm.rwth-aachen.de
> > wrote:
>
>> Hallo,
>>
>> I have a strange behavior in my code concerning the function MatAXPY. I
>> create 3 different Matrices
>>
>> ierr = MatCreateBAIJ(PETSC_COMM_WORLD, block_size, local_size,
>> local_size, system_size, system_size, 0, d_nnz, 0, o_nnz,&A);
>> ierr = MatSetOption(A,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_TRUE);
>> ierr = MatSetOption(A,MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE);
>> ierr = MatSetOption(A,MAT_IGNORE_OFF_PROC_ENTRIES,PETSC_TRUE);
>>
>> ierr = MatCreateBAIJ(PETSC_COMM_WORLD, block_size, local_size,
>> local_size, system_size, system_size, 0, d_nnz, 0, o_nnz,&At);
>> ierr = MatSetOption(At,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_TRUE);
>> ierr = MatSetOption(At,MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE);
>> ierr = MatSetOption(At,MAT_IGNORE_OFF_PROC_ENTRIES,PETSC_TRUE);
>>
>> ierr = MatCreateBAIJ(PETSC_COMM_WORLD, block_size, local_size,
>> local_size, system_size, system_size, 0, d_nnz, 0, o_nnz,&Ah);
>> ierr = MatSetOption(Ah,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_TRUE);
>> ierr = MatSetOption(Ah,MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE);
>> ierr = MatSetOption(Ah,MAT_IGNORE_OFF_PROC_ENTRIES,PETSC_TRUE);
>>
>
> These creations are superfluous since you use MatDuplicate() below.
>
>
>> and want to sum these three matrixes with different factors. First I fill
>> the Matrix A with some values, and duplicate the structure of A to the
>> other two matrices:
>>
>> MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
>> MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
>> MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&Ah);
>> MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&At);
>> MatAssemblyBegin(Ah,MAT_FINAL_ASSEMBLY);
>> MatAssemblyEnd(Ah,MAT_FINAL_ASSEMBLY);
>> MatAssemblyBegin(At,MAT_FINAL_ASSEMBLY);
>> MatAssemblyEnd(At,MAT_FINAL_ASSEMBLY);
>>
>
>
>> After this I fill the matrices At and Ah with some other values, which
>> are not beside the non zero structure (I also tried with just copying the
>> Matrix A). Now after another MatAssembly
>
>
> I do not understand "no beside the nonzero structure". Do you mean that
> the nonzero structure is the same?
>
> Can you first test with MAT_COPY_VALUES?
>
>
>> I want to add these Matrices in the form A+c*(Ah+d*At):
>
>
>> MatAXPY(Ah,c,At,SAME_NONZERO_PATTERN);
>> MatAXPY(A,d,Ah,SAME_NONZERO_PATTERN);
>>
>> When I run the method with mpi and one core everything works fine.
>> Starting the same method with more cores, the sum of the matrices fails. It
>> seems like some values are added
>
>
> Please send the full output of a failure when you use MAT_COPY_VALUES on
> 2 procs.
>
> Thanks,
>
> Matt
>
>
>> correctly and many values are missed. Using DIFFERENT_NONZERO_STRUCTURE
>> leads to the right behavior in the multi-core case, but is very slow. I
>> checked with a viewer if all matrices have the same nonzero structure and
>> this is the case.
>>
>> Does anyone know why this fails, or do I have made any wrong thoughts?
>>
>> I'm corrently working with a petsc version (Petsc Release Version 3.3.0,
>> Patch 5, Sat Dec 1 15:10:41 CST 2012), I looked into the changelogs up to
>> the current version and did not find any note about MatAXPY or MatAYPX.
>>
>>
>> Best and Thanks a lot for your help
>>
>> Klaus
>>
>>
>
>
> --
> 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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