[petsc-users] Sum of the absolute values of each row's components

[Matthew Knepley]

On Mon, May 24, 2021 at 9:08 PM Salazar De Troya, Miguel via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
>
>
> I am simply interested in obtaining a vector with x_i = \sum_j | A_{i, j}
> | for each row “i” in the matrix A. I found MatGetColumnNorms(), but no row
> version. I am wondering if it is more efficient to calculate the transpose
> A^T and then MatGetColumnNorms() or maybe iterate through each row with
> MatGetRow() and calculate \sum_j | A_{i, j} | by hand by myself.
>

Vec ones, sums;

MatCreateVecs(A, &ones, &sums);
VecSet(ones, 1.0);
MatMult(A, ones, sums);
VecDestroy(&ones);
VecDestroy(&sums);

  Thanks,

    Matt


>
>
> Thanks
>
> Miguel
>
>
>
> Miguel A. Salazar de Troya
>
> Postdoctoral Researcher, Lawrence Livermore National Laboratory
>
> B141
>
> Rm: 1085-5
>
> Ph: 1(925) 422-6411
>


-- 
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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