[petsc-users] Question Regarding Duplicate Indices in VecSetValues().

[Matthew Knepley]

On Tue, Jan 14, 2025 at 9:06 AM Mark Adams <mfadams at lbl.gov> wrote:

> INSERT_VALUES is clearly an error, but we can't check that easily so you
> will probably just get the last value, and ADD_VALUES should work.
>

For INSERT_VALUES, it will overwrite with the last value. For ADD_VALUES,
it will add.

  Thanks,

    Matt


> Mark
>
> On Tue, Jan 14, 2025 at 8:20 AM Venkata Narayana Sarma Dhavala <
> dhavala at udel.edu> wrote:
>
>> Dear PETSc Development Team,
>>
>> I hope this message finds you well. I am currently working with the
>> VecSetValues() function in PETSc, and I have a question regarding its
>> behavior when there are duplicate indices in the input array.
>>
>> PetscErrorCode VecSetValues(Vec x, PetscInt ni, const PetscInt ix[],
>> const PetscScalar y[], InsertMode iora)
>>
>> Specifically, what is the expected behavior if the ix[] array passed to
>> VecSetValues() contains duplicate indices? Does the function overwrite the
>> value at those indices, or does it handle duplicates differently depending
>> on the insert mode (INSERT_VALUES or ADD_VALUES)?
>>
>> I would greatly appreciate any clarification on this matter, as it will
>> help me better understand how to manage values when working with
>> potentially repeated indices in the input.
>>
>> Thank you for your time and assistance.
>>
>> Best regards,
>>
>> Narayana Dhavala.
>>
>

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