XANSYS Message: 20621 [Go back to message list]
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Subject: Re: Unsymmetric CG error
Author: Mark Troscinski
Date: 2001-01-30 11:43:00Hi Anh, Mark, & Brad,
After digging in the code, I've determined this error message is associated
with FLOTRAN's PGMR solver, and not the PCG or PCCR solvers.
Normally, I only use PGMR for solving the TEMP DOF matrix, although it is an
available option for the PRES DOF matrix as well.
Mark Troscinski
> -----Original Message-----
> From: Brad Lamirand [SMTP:blamirand@t...]
> Sent: Monday, January 29, 2001 2:21 PM
> To: xansys
> Subject: Re: [xansys] Unsymmetric CG error
> Anh
> This isn't actually a unsymmetric CG error. What is happening is that
> your
> PreConditioned Conjugant Gradient solver (which is the default when
> solving
> incompressible problems) could not reach a converged solution in three
> solver iterations. Although it is ussually the pressure DOF that is
> causing
> this, you should look into your .pfl file to see which DOF(s) are
> diverging.
> To fix this, although it could be a myraid of things, you should check to
> make sure that your boundry conditions are correct and that you don't have
> any unconstrained inlet/outlets.
> Another thing is if you truely have an ill-conditioned problem is to
> change
> the PCCG solver over to the PGMR solver which is more stable and try
> again.
> Hope this helps,
> Brad Lamirand
> Cooper Turbocompressor
> ----- Original Message -----
> From: "Anh Truong"
> To:
> Sent: Monday, January 29, 2001 1:40 PM
> Subject: [xansys] Unsymmetric CG error
> Hello all,
> I got this error message when running FLOTRAN:
> ****************ERROR****
> Unsymmetric CG iterations did not converge three times. The run is
> terminated.
> Does anyone know what an unsymmetric CG error is?
> Thanks muchly,
> Anh