[petsc-users] Finding nonzero indices

[Matthew Knepley]

On Mon, Feb 25, 2019 at 5:25 AM Eda Oktay via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
> I am trying to find the indices (both row and column separately) of
> nonzero entries of a sparse matrix in Petsc Binary Format. I found
> MatGetSeqNonzeroStructure but it gives me a struct and I don't know whether
> this is what I want or not.
>

I would not do it that way, since it is fragile. I would write a loop like
this:

MAtGetOwnershipRange();
for (row = rStart; row < rEnd; ++row) {
  MatGetRow()
  PetscBinaryWrite()
  MatRestoreRow()
}

This will work for any matrix.

    Matt


> Best regards,
>
> Eda
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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