GMRES: Convergence

[Matthew Knepley]

I would guess that you specified a relative tolerance of 10^-8, which
is satisfied below.

   Matt

On 11/19/06, billy at dem.uminho.pt <billy at dem.uminho.pt> wrote:
>
> I have specified maximum number of iterations 500 and tolerance 1E-8. Usually it
> drives the residual to specified tolerance but in this case GMRES seems to stop
> after 15 iterations and the residual is still above tolerance.
>
>   0 KSP Residual norm 2.928143483788e+05
>   1 KSP Residual norm 1.403875955158e+05
>   2 KSP Residual norm 4.068852804332e+04
>   3 KSP Residual norm 8.517044011269e+03
>   4 KSP Residual norm 2.179034005404e+03
>   5 KSP Residual norm 6.155723927227e+02
>   6 KSP Residual norm 1.636241232571e+02
>   7 KSP Residual norm 4.839052750735e+01
>   8 KSP Residual norm 1.118719384434e+01
>   9 KSP Residual norm 3.313977141518e+00
>  10 KSP Residual norm 7.447603108045e-01
>  11 KSP Residual norm 1.942386237492e-01
>  12 KSP Residual norm 4.843647894709e-02
>  13 KSP Residual norm 1.215264193249e-02
>  14 KSP Residual norm 3.111716140560e-03
>  15 KSP Residual norm 7.922640853896e-04
>
> Matrix p Number of iterations: 15 Residual: +7.922641E-04
>
> Anyone knows why this happens?
>
> Billy.
>
>


-- 
"Failure has a thousand explanations. Success doesn't need one" -- Sir
Alec Guiness