[petsc-users] calling both MatSeqAIJSetPreallocation and MatMPIAIJSetPreallocation

[Sam Guo]

Thanks!

On Mon, Jan 11, 2021 at 12:25 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Jan 11, 2021 at 3:00 PM Sam Guo <sam.guo at cd-adapco.com> wrote:
>
>> Dear PETSc Dev Team,
>>    The documentation recommends calling  both of the above preallocation
>> routines for simplicity. Do we waste memory by calling both?
>>
>
> No. Only one will function, depending on the matrix type.
>
>   Thanks,
>
>      Matt
>
>
>> Thanks,
>> Sam
>> MATAIJMATAIJ
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATAIJ.html#MATAIJ> =
>> "aij" - A matrix type to be used for sparse matrices. This matrix type is
>> identical to MATSEQAIJ
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATSEQAIJ.html#MATSEQAIJ> when
>> constructed with a single process communicator, and MATMPIAIJ
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MATMPIAIJ.html#MATMPIAIJ> otherwise.
>> As a result, for single process communicators, MatSeqAIJSetPreallocation
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSeqAIJSetPreallocation.html#MatSeqAIJSetPreallocation> is
>> supported, and similarly MatMPIAIJSetPreallocation
>> <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatMPIAIJSetPreallocation.html#MatMPIAIJSetPreallocation>()
>> is supported for communicators controlling multiple processes. It is
>> recommended that you call both of the above preallocation routines for
>> simplicity.
>>
>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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