Stopping criteria

[Nguyen, Hung V ERDC-ITL-MS]

Hello Matt, 

>however I would first check your matrix using -pc_type lu -ksp_type preonly
to make sure its not singular.

I got the error message below while running with option above. Do I have to
build a matrix with type of seqaij/seqbaij to run with the -pc_type lu
option? 

Thanks,

-Hung



  np ..       138524
  np ..       143882
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: [15]PETSC ERROR: [12]PETSC ERROR: [8]PETSC ERROR:
--------------------- Error Message ------------------------------------
[4]PETSC ERROR: [6]PETSC ERROR: --------------------- Error Message
------------------------------------
[13]PETSC ERROR: --------------------- Error Message
------------------------------------
--------------------- Error Message ------------------------------------
[15]PETSC ERROR: [13]PETSC ERROR: No support for this operation for this
object type!
[12]PETSC ERROR: [15]PETSC ERROR: No support for this operation for this
object type!
No support for this operation for this object type!
[12]PETSC ERROR: Matrix type mpiaij  symbolic LU!
Matrix type mpiaij  symbolic LU!
[13]PETSC ERROR: [15]PETSC ERROR: [12]PETSC ERROR: Matrix type mpiaij
symbolic LU!
[13]PETSC ERROR:
------------------------------------------------------------------------



-----Original Message-----
From: owner-petsc-users at mcs.anl.gov [mailto:owner-petsc-users at mcs.anl.gov] On
Behalf Of Matthew Knepley
Sent: Wednesday, January 14, 2009 2:05 PM
To: petsc-users at mcs.anl.gov
Subject: Re: Stopping criteria

On Wed, Jan 14, 2009 at 1:54 PM, Nguyen, Hung V ERDC-ITL-MS
<Hung.V.Nguyen at usace.army.mil> wrote:



	Hello All,
	
	I tried to solve an ill-conditioned system using cg with Jacobi
	preconditioned. The KSP solver was stopping due to diverged reason
within a
	few iterations. Is there a way to keep KSP solver running until
max_it?


There is no way to continue CG here because it gets a zero divisor, and
interprets this as an indefinite matrix. You can try GMRES, however I would
first check your matrix using -pc_type lu -ksp_type preonly to make sure its
not singular.

  Matt
 


	Thanks,
	
	-hung
	
	hvnguyen:jade23% aprun -n 16 ./test_matrix_read -ksp_type cg -pc_type
jacobi
	-ksp_rtol 1.0e-15 -ksp_max_it 50000 -ksp_monitor
-ksp_converged_reason
	 0 KSP Residual norm 1.379074550666e+04
	 1 KSP Residual norm 7.252034661743e+03
	 2 KSP Residual norm 7.302184771313e+03
	 3 KSP Residual norm 1.162244351275e+04
	 4 KSP Residual norm 7.912531765659e+03
	 5 KSP Residual norm 4.094706251487e+03
	 6 KSP Residual norm 5.486131070301e+03
	 7 KSP Residual norm 6.367904529202e+03
	 8 KSP Residual norm 6.312767173219e+03
	Linear solve did not converge due to DIVERGED_INDEFINITE_MAT
iterations 9
	Time in PETSc solver: 0.452695 seconds
	The number of iteration       = 9
	The solution residual error = 6.312767e+03
	
	




--
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
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