Re: BCGS -ell

[Barry Smith <bsmith@xxxxxxxxxxx>]

On Fri, 9 Jun 2006, Randall Mackie wrote:

> I've been trying the BCGSL KSP solver, and I'm quite impressed as it seems to 
> work
> very well.
>
> When I set a maximum, of say, 3 iterations, I get the following output:
>
>  0 KSP preconditioned resid norm 9.757142002171e-03 true resid norm  3.053549220804e+11
>  2 KSP preconditioned resid norm 9.950207052910e-03 true resid norm  2.907891952886e+11
>  2 KSP preconditioned resid norm 9.504746131013e-03 true resid norm  6.579636683382e+11
                                                                        ^^^^ this is not so good the
residual is getting worse.

> If I use any other KSP method, such as BCGS, I get:
>
>  0 KSP preconditioned resid norm 2.549077299276e-02 true resid norm 
> 3.452610202150e+12
>  1 KSP preconditioned resid norm 1.567856172211e-02 true resid norm 
> 4.186189492208e+11
>  2 KSP preconditioned resid norm 1.591051406166e-02 true resid norm 
> 3.679106968172e+11
>  3 KSP preconditioned resid norm 1.633366526640e-02 true resid norm 
> 3.656300865397e+11
  Hmm, I think it should have the same initial preconditioned residual. The BCGSL
is a "contributed" solver, I don't know much about it.

   Barry
> Is this a bug in the BCGSL routine, or is this the expected behavior?
>
> Thanks, Randy