Further question about PC with Jaocbi Row Sum

[Shi Jin]

Thank you very much.
 

> > Is there something particular about this rowsum method?
> 
>     No. If you use a -ksp_rtol of 1.e-12 and still get different  
> answers, this needs to be investigated.
> 
>

I have tried even with -ksp_rtol   1.e-20 but still got different results.

Here is what I got when solving the mass matrix with 
-pc_type  jacobi
-pc_jacobi_rowsum 1
-ksp_type cg
-sub_pc_type icc
-ksp_rtol 1.e-20
-ksp_monitor
-ksp_view

  0 KSP Residual norm 2.975203858623e+00
  1 KSP Residual norm 2.674371671721e-01
  2 KSP Residual norm 1.841074927355e-01
KSP Object:
  type: cg
  maximum iterations=10000, initial guess is zero
  tolerances:  relative=1e-20, absolute=1e-50, divergence=10000
  left preconditioning
PC Object:
  type: jacobi
  linear system matrix = precond matrix:
  Matrix Object:
    type=seqaij, rows=8775, cols=8775
    total: nonzeros=214591, allocated nonzeros=214591
      not using I-node routines

I realize that the iteration ended when the residual norm is quite large. 
Do you think this indicates something wrong here?

Thank you again.

Shi


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