[petsc-users] Scatter parallel Vec to sequential Vec on non-zeroth process

[Junchao Zhang]

That should work. But VecScatterCreateToZero() is more efficient. So if
possible, better refactor your code in such a way.

--Junchao Zhang

On Wed, Jun 30, 2021 at 7:13 AM Peder Jørgensgaard Olesen via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Dear Matt
>
>
> Thank you for your reply. I'm guessing that the line
>
> if (rank) N = 0;
>
> should be changed to something like
>
> if (rank != target_rank) N = 0;
>
> such that an empty SEQVEC and scatter are created on each rank other than
> target_rank.
>
>
> Med venlig hilsen / Best regards
>
> Peder
> ------------------------------
> *Fra:* Matthew Knepley <knepley at gmail.com>
> *Sendt:* 30. juni 2021 13:58:49
> *Til:* Peder Jørgensgaard Olesen
> *Cc:* petsc-users at mcs.anl.gov
> *Emne:* Re: [petsc-users] Scatter parallel Vec to sequential Vec on
> non-zeroth process
>
> On Wed, Jun 30, 2021 at 6:49 AM Peder Jørgensgaard Olesen via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>> Hello
>>
>>
>> I have a parallel vector, and I'd like to copy its data to a sequential
>> vector located on a given process that is not necessarily the
>> 0th process, so using VecScatterCreateToZero wouldn't do here.
>>
>>
>> How might one approach this?
>>
> The function is very short:
> https://www.mcs.anl.gov/petsc/petsc-current/src/vec/is/sf/interface/vscat.c.html#VecScatterCreateToZero
> Just go in and replace '0' by the rank you want.
>
>   Thanks,
>
>      Matt
>
>> Med venlig hilsen / Best Regards
>>
>>
>> Peder Jørgensgaard Olesen
>>
>> PhD Student, Turbulence Research Lab
>>
>> Dept. of Mechanical Engineering
>>
>> Technical University of Denmark
>>
>> Koppels Allé
>>
>> Bygning 403, Rum 105
>>
>> DK-2800 Kgs. Lyngby
>>
>
>
> --
> 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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