bratu2dnpy.py does not "return f", instead it modifies the argument f by
manipulating its internal array.
If you want to use a function that "return f" you have to receive this returned
variable and then set it to the Vec object, i.e.:
f = self.compute(expected_soln_vec_npy, x, f)
F.setArray(f)
Jose
> El 26 oct 2024, a las 12:39, Vaishak Prasad <[email protected]>
> escribió:
>
> Dear Jose,
>
> Thankyou very much for your response.
>
> On Sat, Oct 26, 2024 at 3:32 PM Jose E. Roman <[email protected]> wrote:
> Your residue() function is computing something (f) that is not returned to
> the calling function. So evalFunction() returns a zero residual and the
> solver stops in one iteration.
> Apologies, I am a little confused. The example bratu2d.py imports the residue
> function from bratu2dnpy.py and it also does not return anything (and it
> works). I was under the impression that
> a pointer to `f` is passed to petsc, that overwrites it at each iteration.
> Please correct me if I am wrong.
>
> I also tried returning `f` in my residue function but it does not change
> anything. Is this what you suggested?
> Mixing numpy arrays and petsc4py vectors is going to be tricky unless you
> know what you are doing. It is simpler to manipulate petsc4py vectors
> directly, see for instance bratu3d.py or other examples.
> I have also tried this. I created a petsc vector for the input expected
> solution and then converted it into a numpy array using the `getArray`
> method. But noting changes.
>
> I also printed some information about the convergence itself. I find
> ConvergedReason is 2 (absolute tolerance)
> getTolerances is [1e-8, 1e-50, 1e-8, 50] (default)
> getErrorIfNotConverged is False
> getIterationNumber is 0
>
> In contrast, the convergence reason for the bratu2d example was 3 (relative
> tolerance).
>
> I also tried increasing the `max_it` but to no avail.
>
> I appreciate your valuable suggestion and advice in this regard.
>
> Thanks and Regards
>
> Jose
>
>
> > El 26 oct 2024, a las 11:11, Vaishak Prasad <[email protected]>
> > escribió:
> >
> > Hi,
> >
> > Thanks for pointing me to the updated example. The example itself works
> > fine.
> >
> > However, on adapting the example to a simple problem ( recovering a given
> > 1D vector), I find that there is only one function call happening and the
> > solution has not converged. I am attaching the modified example here. Is
> > there something silly I am doing here?
> >
> > Any help would be appreciated.
> >
> > Thanks and Regards
> >
> >
> > On Sat, Oct 26, 2024 at 12:42 PM Jose E. Roman <[email protected]> wrote:
> > The examples in those old slides might be outdated. Try with the examples
> > that come with the PETSc repo or tarball. In particular, that example can
> > be found in src/binding/petsc4py/demo/legacy/bratu2d/bratu2d.py.
> >
> > Jose
> >
> > > El 25 oct 2024, a las 19:58, Vaishak Prasad <[email protected]>
> > > escribió:
> > >
> > > Dear All,
> > > Greetings from India.
> > >
> > > I am new to petsc4py. I was trying out the example on slides 18, and 19 at
> > >
> > > https://urldefense.us/v3/__https://www.bu.edu/pasi/files/2011/01/Lisandro-Dalcin-petsc4py.pdf__;!!G_uCfscf7eWS!ZnQ15XH0wdJTgAhkpejZ0TFFnvrfoV8_YNfEnMmNV9HbN5jMiA0BcE2ru-OzhnPQxY5rps05o84vIoA9rvUd4pK3$
> > >
> > >
> > > However, I get a zero vector for the solution `x`.
> > >
> > > I am using petsc4py 3.21.3 on Linux.
> > >
> > > Any help would be appreciated.
> > >
> > > With regards
> > >
> > > --
> > > Vaishak Prasad
> > > Post Doctoral Fellow
> > > Astrophysical Relativity Group
> > > International Center for Theoretical Sciences
> > > Tata Institute of Fundamental Research
> > > Survey No. 151, Shivakote, Hesaraghatta Hobli,
> > > Bengaluru, Karnataka, India,
> > > Earth, Solar system,
> > > Milky Way Galaxy, The Local Group
> >
> >
> >
> > --
> > Vaishak Prasad
> > Post Doctoral Fellow
> > Astrophysical Relativity Group
> > International Center for Theoretical Sciences
> > Tata Institute of Fundamental Research
> > Survey No. 151, Shivakote, Hesaraghatta Hobli,
> > Bengaluru, Karnataka, India,
> > Earth, Solar system,
> > Milky Way Galaxy, The Local Group
> > <mwe.py>
>
>
>
> --
> Vaishak Prasad
> Post Doctoral Fellow
> Astrophysical Relativity Group
> International Center for Theoretical Sciences
> Tata Institute of Fundamental Research
> Survey No. 151, Shivakote, Hesaraghatta Hobli,
> Bengaluru, Karnataka, India,
> Earth, Solar system,
> Milky Way Galaxy, The Local Group<mwe.py>
