[petsc-users] petsc4py, plotting DA and writing to file

[Lisandro Dalcin]

On 27 September 2010 13:33, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>  Lisandro
>
>    In C he could do VecView(vec,PETSC_VIEWER_DRAW_WORLD); can he not do the equivalent in Python?
> What syntax would he use?

viewer = PETSc.Viewer.DRAW(globalvec.comm)
globalvec.view(viewer) # or viewer(globalvec)

>
> Perhaps the 2d bratu python example could demonstrate this since it is simple and there is no monkeying with copying to one process etc.
>

Well, that example does not even use a DA, the plot is going to be a bit ugly.

>   Barry
>
> On Sep 27, 2010, at 11:27 AM, Lisandro Dalcin wrote:
>
>> On 27 September 2010 13:12, Amal Alghamdi <amal.ghamdi at kaust.edu.sa> wrote:
>>> Dear All,
>>> I'm using the DA structure in petsc4py. I'd like to know please what is the
>>> right way to:
>>> plot the DA vector (the global vector).
>>> write the global vector to a file.
>>> Is that each process writes or draws its own part? or I should communicate
>>> all the data to one process? or none of these?!!
>>> Thank you very much
>>> Amal
>>
>> Use a PETSc.Viewer().createBinary() to save the global vector. Each
>> process will save its own part.
>>
>> In order to plot it, I think you should use numpy.fromfile() to load
>> the data, and then plot the array.
>>
>> Other way would be to use a PETSc.Scatter.toZero() to get the data at
>> process 0, and then plot it
>>
>> scatter, seqvec = PETSc.Scatter.toZero(globalvec)
>> im = PETSc.InsertMode.INSERT_VALUES
>> sm = PETSc.ScatterMode.FORWARD
>> scatter.scatter(globalvec, seqvec, im, sm)
>> if globalvec.comm.rank == 0:
>>    plot(seqvec.array)
>>
>>
>> --
>> Lisandro Dalcin
>> ---------------
>> CIMEC (INTEC/CONICET-UNL)
>> Predio CONICET-Santa Fe
>> Colectora RN 168 Km 472, Paraje El Pozo
>> Tel: +54-342-4511594 (ext 1011)
>> Tel/Fax: +54-342-4511169
>
>



-- 
Lisandro Dalcin
---------------
CIMEC (INTEC/CONICET-UNL)
Predio CONICET-Santa Fe
Colectora RN 168 Km 472, Paraje El Pozo
Tel: +54-342-4511594 (ext 1011)
Tel/Fax: +54-342-4511169