[petsc-users] DMDA3D with custom preallocation leads to MAT_NEW_NONZERO_ALLOCATION_ERR when using pc_gamg

[Fabian.Jakub]

I'm sorry, I just remembered... this may be important to know...

call KSPCreate(imp_comm,ksp,ierr)

call KSPSetOperators(ksp,A,A,ierr)
call KSPSetDM(ksp,C%da,ierr)
call KSPSetDMActive(ksp,PETSC_FALSE,ierr)

call KSPSetFromOptions(ksp,ierr)
call KSPSetUp(ksp,ierr)

Thanks again...


Am 08.07.2014 14:39, schrieb Fabian.Jakub:
> Hi,
> I have a question regarding gamg where I get a wrong preallocation 
> i.e. a  MAT_NEW_NONZERO_ALLOCATION_ERR **.
>
> I use a 3d DMDA with 10 dof but the coupling only ever needs 2 dof on 
> a star stencil.
>
> The code to setup the matrix is like this:
>
> call DMSetMatrixPreallocateOnly(C%da, PETSC_TRUE,ierr)
> call DMCreateMatrix(C%da, A, ierr)
> call MatSetFromOptions(A,ierr)
>
> call MatMPIAIJSetPreallocation(A, PETSC_NULL_INTEGER,d_nnz, 
> PETSC_NULL_INTEGER, o_nnz, ierr)
>
> insert matrix values & assemble
>
> then solve.
>
> If I solve the system with any ''normal'' KSP/PC there is no problem 
> and matrix info actually confirms that the preallocation is good.
> However if I use gamg I get an allocation error when it tries to 
> create a coarse grid.
>
> If I use the DMDA preallocation, it works but uses way more memory...
>
> Is there a possibility to use custom preallocation and at the same 
> time let gamg create the coarse grid?
> Is that even the problem or am I missing something?
>
> Thank you so very much.
>
> Sincerely,
> Fabian
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