[petsc-users] Convergence behavior of different solvers

[Jed Brown]

On Wed, Mar 21, 2012 at 04:03, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:

> Hello,
>
> Plotting values of relative residual norm versus iteration I noticed that
> these curves have different behavior. For instance, ones I got with
> BiCGStab are oscillatory and rather noisy with large jumps within few
> iterations. Curves for QMR are smooth, however it's usual that they
> stagnate for ~10-20 iterations and then go down further. Same
> preconditioner is applied for both and both methods are Lanczos based, so I
> don't understand this.
> I'm wondering is this just my specific case or there is general
> explanation for that?
>

This is normal.

http://people.maths.ox.ac.uk/trefethen/publication/PDF/1992_52.pdf
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