[petsc-users] KSP solver increases the solution time

[Jed Brown]

2011/4/26 Alejandro Marcos Aragón <alejandro.aragon at gmail.com>

> Hi Jed, thanks for replying. In fact, the problem I sent the results from
> is a dynamic problem of a simply supported beam subjected to a constant load
> at the center, so I'm integrating in time.
>

I take it there is no buckling.


> The material is linear elastic so the stiffness matrix doesn't change in
> non-zero structure. Of course the right hand side changes, but I don't think
> this is the problem because at some point it takes it goes back to just a
> few iterations to solve. The behavior is cyclic, but I don't understand the
> reason for this. I've noticed the same behavior of the solver also in
> quasi-static problems (increasing the load gradually but not integrating
> over time).
>

Is the convergence relatively smooth? Are you losing a lot in GMRES restarts
(every 30 iterations)? If you have a symmetric formulation (including
boundary conditions), you can use -ksp_type cg, otherwise try
-ksp_gmres_restart 500.

Also, try solving the system with a random right hand side.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110426/28e15076/attachment.htm>