[petsc-users] Parallel vector with shared memory in Fortran

[Matthew Knepley]

On Mon, Jun 5, 2017 at 11:20 AM, Francesco Migliorini <
francescomigliorini93 at gmail.com> wrote:

> Dear Stefano,
> Thank you for your answer. I tried to use VecScatterCreateToAll as you
> suggested but it does not work since the first processor can only view its
> part of the vector.
>

Then there is a bug in your code. The
example src/vec/vec/examples/tests/ex33.c tests this. Take a look at it.

  Thanks,

     Matt


> Here's how I managed the code:
>
> Vec    fePS
> VecScatter    Scatter
> (...)
> call VecScatterCreateToAll(feP,Scatter,fePS,perr)
> call VecScatterBegin(Scatter,feP,fePS,INSERT_VALUES,SCATTER_FORWARD,perr)
> call VecScatterEnd(Scatter,feP,fePS,INSERT_VALUES,SCATTER_FORWARD,perr)
> call VecScatterDestroy(Scatter,perr)
> call VecDestroy(fePS,perr)
>
> As I said, after this piece of code, if I print all the entries of feP
> from one processor, the values are correct if they belong to the part of
> the processor randon values.
>
> Bests,
> Francesco
>
> 2017-06-05 16:44 GMT+02:00 Stefano Zampini <stefano.zampini at gmail.com>:
>
>> Sorry, bad copy and paste
>>
>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/
>> Vec/VecScatterCreateToAll.html
>>
>> Il 05 Giu 2017 4:43 PM, "Stefano Zampini" <stefano.zampini at gmail.com> ha
>> scritto:
>>
>>> petsc-current/docs/manualpages/Vec/VecScatterCreateToAll.html
>>>
>>> Il 05 Giu 2017 4:12 PM, "Francesco Migliorini" <
>>> francescomigliorini93 at gmail.com> ha scritto:
>>>
>>>> Hello there!
>>>>
>>>> I am working with an MPI code in which I should create a petsc vector
>>>> such that all the processes can access to all its entries. So, I tried with
>>>> VecCreateShared but it does not work with my machine. Then I tried
>>>> VecCreateMPI but it seems to me that it does not change anything from the
>>>> usual VecCreate. Finally I found the scatter commands but the examples are
>>>> a bit tricky. So, are there any other way? If no, could someone please show
>>>> me how to use scatter in this simple code?
>>>>
>>>> Vec  feP    !The vector to be shared with all the processes
>>>> (...)
>>>> mpi_np = 2    !The number of processes
>>>> ind(1) = 10   !The global dimension of the vector
>>>> call VecCreate(PETSC_COMM_WORLD,feP,perr)
>>>> call VecSetSizes(feP,PETSC_DECIDE,ind,perr)
>>>> call VecSetFromOptions(feP,perr)
>>>> (...)    !Here feP is filled in
>>>> call VecAssemblyBegin(feP,perr)
>>>> call VecAssemblyEnd(feP,perr)
>>>>
>>>> Many thanks,
>>>> Francesco
>>>>
>>>
>


-- 
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

http://www.caam.rice.edu/~mk51/
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