[petsc-users] Nodes Communication - Petsc Vec

[Medane TCHAKOROM]

Re:

Please, could you if possible, provide a basic example code. I do not 
understand how to "go to the supercommunicator, incorporating these two 
groups and use VecScatter"

Another question is: If I was to use "MPI calls", can I use Petsc Vec as 
a buffer ? If so, which type should I indicate (MPI_Datatype) in the 
let's say MPI_Isend method ?

Thanks

On 16/02/2022 15:48, Matthew Knepley wrote:
> On Wed, Feb 16, 2022 at 9:47 AM Medane TCHAKOROM 
> <medane.tchakorom at univ-fcomte.fr> wrote:
>
>     Re:
>
>
>     It does not apply, because "their communicator must be on the same
>     set of processes" .
>
>     In my case, I have two disjoint subcomm from PETSC_COMM_WORD with
>     same number of processes.
>
>     I want to send information (Petsc Vec) from one subcomm to another
>     subcomm.
>
> The way I do this is to go to the supercommunicator, incorporating 
> these two groups and use VecScatter.
> The alternative is just to use custom MPI calls as you say.
>
>   Thanks,
>
>      Matt
>
>     Thanks
>
>     On 16/02/2022 15:43, Junchao Zhang wrote:
>>     See Notes at
>>     https://petsc.org/main/docs/manualpages/PetscSF/VecScatterCreate.html
>>
>>
>>     Does it apply to your case?
>>
>>     --Junchao Zhang
>>
>>
>>     On Wed, Feb 16, 2022 at 8:12 AM Medane TCHAKOROM
>>     <medane.tchakorom at univ-fcomte.fr> wrote:
>>
>>         Re:
>>
>>         I forgot to mention that the nodes are in differents
>>         communicators. Does VecScatter functionnality still applies ?
>>
>>         Thanks.
>>
>>         On 16/02/2022 15:03, Matthew Knepley wrote:
>>>         On Wed, Feb 16, 2022 at 8:55 AM Medane TCHAKOROM
>>>         <medane.tchakorom at univ-fcomte.fr> wrote:
>>>
>>>             Hello,
>>>
>>>             I want to pass a Petsc Vec from one node to another one.
>>>             Is there any
>>>             Petsc method for doing this
>>>
>>>
>>>         You likely want the VecScatter functionality. There is a
>>>         discussion of this in the manual:
>>>         https://petsc.org/main/docs/manual/vec/?highlight=vecscatter#sec-unstruct
>>>
>>>           Thanks,
>>>
>>>             Matt
>>>
>>>             or should I use MPI_Irecv and MPI_Isend for non-blocking
>>>             communication ?
>>>
>>>             When using MPI_Isend, can i send a Petsc Vec, or should
>>>             I get the array
>>>             from it, and then send it ?
>>>
>>>             Thanks
>>>
>>>
>>>
>>>         -- 
>>>         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/>
>>
>
>
> -- 
> 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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