[petsc-users] Equivalent of all_reduce for sparse matrices

[Jed Brown]

marco restelli <mrestelli at gmail.com> writes:
> Matt, thanks but this I don't understand. What I want is getting three
> arrays (i,j,coeff) with all the nonzero local coefficients, so that I
> can send them around with MPI.
>
> MatGetSubmatrices would give me some PETSc objects, which I can not
> pass to MPI, right?

I'm not sure you want this, but you can use MatGetRowIJ and similar to
access the representation you're asking for if you are dead set on
depending on a specific data format rather than using generic
interfaces.
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