[petsc-users] Weighted Jacobi, and scaling 2nd matrix in KSPSetOperators

Dave May dave.mayhem23 at gmail.com
Mon Feb 22 16:28:28 CST 2016

On 22 February 2016 at 23:16, Timothée Nicolas <timothee.nicolas at gmail.com>

> Hi all,
> It sounds it should be obvious but I can't find it somehow. I would like
> to use weighted jacobi (more precisely point block jacobi) as a smoother
> for multigrid, but I don't find the options to set a weight omega, after I
> set -mg_levels_pc_type pbjacobi

Why not use  -ksp_type richardson -ksp_richardson_scale XXX ?


So I was thinking I could just artificially scale the second matrix in
> KSPSetOperators with a weight omega. Since it is the one used in retrieving
> the diagonal, it should be equivalent to have a weight and should not
> affect the residuals, right ? However, I notice no change of behaviour
> whatsoever when I do this.
> Is it normal ? Have I grossly misunderstood something ?
> Thanks
> Timothee
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