[petsc-users] The condition number

[Barry Smith]

  With this type of condition number estimator there is no certainty that this is exactly correct, it may be a bit higher but likely this is a good estimate of the condition number.

   Barry

On Feb 5, 2013, at 1:27 PM, w_ang_temp <w_ang_temp at 163.com> wrote:

> Hello,
> I want to get the condition number of the matrix. I use the command:
>  mpiexec -n 1 ./ex4f -ksp_type gmres -pc_type none -ksp_monitor_singular_value -ksp_gmres_restart 10000
> The information is:
> 287 KSP Residual norm 2.709682524692e-05 % max 2.926321440259e+04 min 5.402536868919e-01 max/min 5.416569125321e+04
> 288 KSP Residual norm 2.519306234382e-05 % max 2.926321440259e+04 min 5.266603977255e-01 max/min 5.556372669936e+04
> 289 KSP Residual norm 2.378149039323e-05 % max 2.926321440259e+04 min 5.172748873301e-01 max/min 5.657188299559e+04
> 290 KSP Residual norm 2.287472821678e-05 % max 2.926321440260e+04 min 5.115884179685e-01 max/min 5.720069762095e+04
> 291 KSP Residual norm 2.228155716304e-05 % max 2.926321440260e+04 min 5.080217090257e-01 max/min 5.760229116728e+04
> 292 KSP Residual norm 2.192114571943e-05 % max 2.926321440260e+04 min 5.059182789026e-01 max/min 5.784178121826e+04
> 293 KSP Residual norm 2.167188877219e-05 % max 2.926321440260e+04 min 5.044948817455e-01 max/min 5.800497777371e+04
> 294 KSP Residual norm 2.148234628716e-05 % max 2.926321440260e+04 min 5.034325309589e-01 max/min 5.812738073732e+04
> 295 KSP Re sidual norm 2.132127329266e-05 % max 2.926321440260e+04 min 5.025455984087e-01 max/min 5.822996857452e+04
> 296 KSP Residual norm 2.113112645062e-05 % max 2.926321440260e+04 min 5.015166226585e-01 max/min 5.834944063764e+04
> Linear solve converged due to CONVERGED_RTOL iterations 296
>  
> So is the condition number: max/min 5.834944063764e+04? The value of the last iteration?
> Thanks.
>                                              Jim
> 
>