KSPSkipConverged

[Lisandro Dalcin]

On 8/28/07, Matthew Knepley <knepley at gmail.com> wrote:
> Yes, definitely. Go ahead and push it.

I started to try this by implementing first on petsc4py with
petsc-2.3.3-p4, by solving a trivial SPD diagonal system { A_ii =
1/(i+1) } with no PC and maxit=5. Below the results, some things seems
broken.

I think I will do the following:

1- Correct things in release-2.3.3, KSP's should not set
KSP_DIVERGED_ITS if the convergence test returned other than
KSP_CONVERGED_ITERATING (all GMRES's, RICHARDSON and TCQMR seems to do
this). It also seems that I have to review KSP type GLTR (it stopped
at iteration 4 and not 5, as it should).

2- Modify KSPSkipConverged and push on petsc-dev. Or perhpas can we
also push this on release-2.3.3? The previous way is rather buggy,
especially in conjunction with KSP_NORM_NO.

Below the result (petsc4py is a nice tool for test/debug, isn't it?)


tfqmr      - CONVERGED_ITS        - iters:   5, ||r|| = 4.881889e-03,
x0,N-1=0.999996,9.978373
minres     - CONVERGED_ITS        - iters:   5, ||r|| = 5.356222e-02,
x0,N-1=1.000009,9.701171
fgmres     - DIVERGED_ITS         - iters:   5, ||r|| = 5.356222e-02,
x0,N-1=1.000009,9.701171
stcg       - CONVERGED_ITS        - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
qcg        - CONVERGED_ITS        - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=-1.000052,-9.771470
cg         - CONVERGED_ITS        - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
lgmres     - DIVERGED_ITS         - iters:   5, ||r|| = 5.356222e-02,
x0,N-1=1.000009,9.701171
cgne       - CONVERGED_ITS        - iters:   5, ||r|| = 7.192229e-02,
x0,N-1=1.000000,7.116166
chebychev  - DIVERGED_ITS         - iters:   5, ||r|| = 2.591834e+00,
x0,N-1=0.636559,0.708271
cgs        - CONVERGED_ITS        - iters:   5, ||r|| = 1.457830e-03,
x0,N-1=1.000000,9.994777
bicg       - CONVERGED_ITS        - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
lsqr       - CONVERGED_ITS        - iters:   5, ||r|| = 4.612376e-01,
x0,N-1=1.000000,7.116166
gltr       - CONVERGED_ITS        - iters:   4, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
tcqmr      - DIVERGED_ITS         - iters:   5, ||r|| = 0.000000e+00,
x0,N-1=1.000009,9.701171
bcgs       - CONVERGED_ITS        - iters:   5, ||r|| = 2.566301e-03,
x0,N-1=0.999703,9.982615
cr         - CONVERGED_ITS        - iters:   5, ||r|| = 5.356222e-02,
x0,N-1=1.000009,9.701171
symmlq     - CONVERGED_ITS        - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
bcgsl      - CONVERGED_ITS        - iters:   5, ||r|| = 1.232695e-03,
x0,N-1=0.999988,9.999315
lcd        - DIVERGED_ITS         - iters:   5, ||r|| = 5.629995e-02,
x0,N-1=1.000052,9.771470
preonly    - CONVERGED_ITS        - iters:   1, ||r|| = 0.000000e+00,
x0,N-1=1.000000,1.000000
gmres      - DIVERGED_ITS         - iters:   5, ||r|| = 5.356222e-02,
x0,N-1=1.000009,9.701171
richardson - DIVERGED_ITS         - iters:   5, ||r|| = 1.215430e+00,
x0,N-1=1.000000,4.095100




>
> On 8/28/07, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> > Does it make sense to change KSPSkipConverged to return
> > KSP_CONVERGED_ITS if  iternum==maxit ?
> >
> > KSP_DIVERGED_ITS means convergence failure, but IMHO, KSPSkipConverged
> > should not imply convergence failure (this has implications in SNES).
> >
> >
> > --
> > Lisandro Dalcín
> > ---------------
> > Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> > Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> > Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> > PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> > Tel/Fax: +54-(0)342-451.1594
> >
> >
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which
> their experiments lead.
> -- Norbert Wiener
>
>


-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594