> On Jul 15, 2025, at 8:13 AM, SCOTTO Alexandre via petsc-users
> <petsc-users@mcs.anl.gov> wrote:
>
> Hello Jose,
>
> Thanks for your answer. Then it seems that I have under the hood usages of
> setValues() in my code since I do not explicitly make use of it but still has
> problems when not assembling my vector. Do I need to assemble vectors after
> Mat.mult or Scatter.scatter?
Absolutely not. In such situations all the communication and putting the
correct vector values in the correct location is done automatically by the
routines you are calling.
>
> By the way, I did not know that PETSc.Vec objects supported direct
> assignments like x[i] = ..., so I rather use assignments of the form x.array
> = ...
>
> From what I understand from the GitHub page
> (https://urldefense.us/v3/__https://gitlab.com/petsc/petsc/-/blob/main/src/binding/petsc4py/src/petsc4py/PETSc/Vec.pyx__;!!G_uCfscf7eWS!f3M5SmfhSqew4tgfvFDjdLnd3q3kT_KzcCitJTJC0HRl1YvbSNBr5Uuzv6OWP1pVQBgbi_WJlekerylpGcBHQ9vsbzL1suFBQHkoPIwhdw$
> ) it seems, that doing so, we only access the local portion of the array
> which should not require any assemble() am I right?
>
> Best regards,
> Alexandre.
>
>
> -----Message d'origine-----
> De : Jose E. Roman <jro...@dsic.upv.es>
> Envoyé : mardi 15 juillet 2025 12:21
> À : SCOTTO Alexandre <alexandre.sco...@irt-saintexupery.com>
> Cc : petsc-users@mcs.anl.gov
> Objet : Re: [petsc-users] When to perform PETSc.Vec assembly with petsc4py
>
> Assembly is needed after a call to x.setValues() or any of its variants.
> https://urldefense.us/v3/__https://petsc.org/main/petsc4py/reference/petsc4py.PETSc.Vec.html*petsc4py.PETSc.Vec.setValue__;Iw!!G_uCfscf7eWS!f3M5SmfhSqew4tgfvFDjdLnd3q3kT_KzcCitJTJC0HRl1YvbSNBr5Uuzv6OWP1pVQBgbi_WJlekerylpGcBHQ9vsbzL1suFBQHlKEPOyQg$
>
> Take into account that in python the notation x[i] = ... with call
> x.setValues() under the hood.
>
> Jose
>
>
>> El 15 jul 2025, a las 12:02, SCOTTO Alexandre via petsc-users
>> <petsc-users@mcs.anl.gov> escribió:
>>
>> Dear PETSc community,
>> As a beginner in the MPI world and with the PETSc library, I come with a
>> possibly very naive question.
>> I know from the documentation that assembling vectors must be done, but it
>> is not clear to me when to perform this operation.
>> Is there a simple way to know when a vector need be assembled and when it is
>> not?
>> Thanks in advance.
>> Regards,
>> Alexandre.
>
