[petsc-users] Problem with MPI, MatAXPY and SAME_NONZERO_PATTERN
Klaus Kaiser
kaiser at igpm.rwth-aachen.de
Fri Mar 27 10:16:48 CDT 2015
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.
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 <mailto: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
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