[petsc-users] Petsc has generated inconsistent data - Divide by zero!

[Jed Brown]

On Fri, Jul 8, 2011 at 17:17, TAY wee-beng <zonexo at gmail.com> wrote:

> **
> Hi Jed,
>
> This is my output when the error happens for gmres:
>
>   2 KSP preconditioned resid norm 1.556688898463e+007 true resid norm
> 2.58995443
> 8801e+003 ||Ae||/||Ax|| 1.232088736212e+003
>   2 KSP preconditioned resid norm 1.556688898463e+007 true resid norm
> 2.58995443
> 8801e+003 ||Ae||/||Ax|| 1.232088736212e+003
>   3 KSP preconditioned resid norm 1.207952812560e+003 true resid norm
> 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
>   3 KSP preconditioned resid norm 1.207952812560e+003 true resid norm
> 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003 3 KSP preconditioned resid norm
> 1.207952812560e+003 true resid norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
>   3 KSP preconditioned resid norm 1.207952812560e+003 true resid norm
> 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
>   3 KSP preconditioned resid norm 1.207952812560e+003 true resid norm
> 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
>   4 KSP preconditioned resid norm 3.815055004710e+001 true resid norm
> 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>   4 KSP preconditioned resid norm 3.815055004710e+001 true resid norm
> 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>   4 KSP preconditioned resid norm 3.815055004710e+001 true resid norm
> 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>   4 KSP preconditioned resid norm 3.815055004710e+001 true resid norm
> 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>   4 KSP preconditioned resid norm 3.815055004710e+001 true resid norm
> 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>

Why is the same line output multiple times? Do you have an MPI problem?

This convergence looks funky; I suspect your preconditioner is singular
and/or nonlinear. Please send -ksp_view output as you are running here and
with -pc_type asm -sub_pc_type lu.


>
> for fgmres:
>
>  34 KSP preconditioned resid norm 2.428114102327e-005 true resid norm
> 3.35941610
> 6265e-005 ||Ae||/||Ax|| 1.598129588716e-005
>  34 KSP preconditioned resid norm 2.428114102327e-005 true resid norm
> 3.35941610
> 6265e-005 ||Ae||/||Ax|| 1.598129588716e-005
>  35 KSP preconditioned resid norm 2.200715659545e-005 true resid norm
> 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
>  35 KSP preconditioned resid norm 2.200715659545e-005 true resid norm
> 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
>  35 KSP preconditioned resid norm 2.200715659545e-005 true resid norm
> 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
>  35 KSP preconditioned resid norm 2.200715659545e-005 true resid norm
> 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
>  35 KSP preconditioned resid norm 2.200715659545e-005 true resid norm
> 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
>  36 KSP preconditioned resid norm 2.011575409369e-005 true resid norm
> 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>  36 KSP preconditioned resid norm 2.011575409369e-005 true resid norm
> 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>  36 KSP preconditioned resid norm 2.011575409369e-005 true resid norm
> 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>  36 KSP preconditioned resid norm 2.011575409369e-005 true resid norm
> 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>  36 KSP preconditioned resid norm 2.011575409369e-005 true resid norm
> 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>
> Btw, I am solving the x and y momentum eqns so there 's 2 eqns to solve.
>

Do you solve them separately or both at once? (We usually recommend the
latter.)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110708/136cffd5/attachment.htm>