[petsc-users] [petsc-3.2] LSQR new convergence test

[Barry Smith]

It has its own monitor that provides additional information  -ksp_monitor_lsqr

You can also remove the new convergence test and get back the old one with code like

void *cctx;
KSPDefaultConvergedCreate(&cctx);
KSPSetConvergenceTest(ksp,KSPDefaultConverged,cctx);

after the KSPType is set to LSQR. So if you are happy with the old test. 


  Do both versions give the same first two norms?

> 0 KSP Residual norm 9.386670021557e-17
>  1 KSP Residual norm 8.258308650175e-17

  Barry


On Sep 20, 2011, at 4:40 AM, Alexander Grayver wrote:

> Hello,
> 
> In comparison with petsc-3.1-p7 in the latest petsc LSQR solver behaves differently.
> 
> In petsc31 I had:
> 
>  0 KSP Residual norm 9.386670021557e-17
> ...
> 95 KSP Residual norm 9.341367317075e-18
> Linear solve converged due to CONVERGED_RTOL iterations 95
> KSP Object:
>  type: lsqr
>  maximum iterations=200, initial guess is zero
>  tolerances:  relative=0.1, absolute=1e-50, divergence=10000
>  left preconditioning
>  using PRECONDITIONED norm type for convergence test
> PC Object:
>  type: none
>  linear system matrix = precond matrix:
>  Matrix Object:
>    type=shell, rows=19584, cols=19584
> 
> relative residual norm =    0.9951737192872134E-01
> 
> Now, with petsc32 I have:
> 
>  0 KSP Residual norm 9.386670021557e-17
>  1 KSP Residual norm 8.258308650175e-17
> Linear solve converged due to CONVERGED_RTOL_NORMAL iterations 1
> KSP Object: 12 MPI processes
>  type: lsqr
>  maximum iterations=200, initial guess is zero
>  tolerances:  relative=0.1, absolute=1e-50, divergence=10000
>  left preconditioning
>  using UNPRECONDITIONED norm type for convergence test
> PC Object: 12 MPI processes
>  type: none
>  linear system matrix = precond matrix:
>  Matrix Object:   12 MPI processes
>    type: shell
>    rows=19584, cols=19584
> relative residual norm =    0.8797910900468064E+00
> 
> So I found new convergence test here which sets CONVERGED_RTOL_NORMAL:
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPLSQRDefaultConverged.html
> 
> The question is, how to interpret this new test and make it works properly for me?
> Thanks in advance.
> 
> Regards,
> Alexander