[petsc-users] Equivalent of all_reduce for sparse matrices

[Matthew Knepley]

On Thu, May 8, 2014 at 11:25 AM, marco restelli <mrestelli at gmail.com> wrote:

> Hi,
>    I have a Cartesian communicator and some matrices distributed along
> the "x" direction. I would like to compute an all_reduce operation for
> these matrices in the y direction, and I wander whether there is a
> PETSc function for this.
>
>
> More precisely:
>
> a matrix A is distributed among processors  0 , 1 , 2
> another A is distributed among processors   3 , 4 , 5
> another A is distributed among processors   6 , 7 , 8
> ...
>
> The x direction is 0,1,2; while the y direction is 0,3,6,...
>
> I would like to compute a matrix  B = "sum of the matrices A"  and a
> copy of B should be distributed among processors 0,1,2, another copy
> among 3,4,5 and so on.
>
> A way of doing this is getting the matrix coefficients, broadcasting
> them along the y direction and summing them in the matrix B; maybe
> however there is already a PETSc function doing this.
>

There is nothing like this in PETSc. There are many tools for this using
dense
matrices in Elemental, but I have not seen anything for sparse matrices.

   Matt


> Thank you, regards
>    Marco
>



-- 
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
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