[petsc-users] questions about KSP with-pc_type hypre

[Roc Wang]

Sorry for the mis-info. 

Yes, I have Dirichlet BCs. The  smaller round plate on the left side and the rectangular plane on the right size are the Dirichlet BCs. And the inside the hole of the rectangular plane is Neumann BCs.  I am just wondering the Neumann BCs of the hole have some effect which lead to divergence.  

I will try gamg as your suggestion. Thanks.


Subject: Re: [petsc-users] questions about KSP with-pc_type hypre
From: mfadams at lbl.gov
Date: Mon, 7 Oct 2013 16:16:30 -0400
CC: petsc-users at mcs.anl.gov
To: pengxwang at hotmail.com

I assume this is a Lapacian and its not a pure Neumann problem.  I did not quite follow you description.  Do you have some Dirichlet BCs?
Hypre is a very robust solver, for a scalable solver.  ILU, the default PC, is very robust but slow (that's why its the default).  You could try gamg, another AMG solver to get another data point.
On Oct 7, 2013, at 3:08 PM, Roc Wang <pengxwang at hotmail.com> wrote:Hello,

   I am trying to solve a linear system with KSP for a 3-D domain.  The computational domain is a cubic space with Neumann condition on the lateral sides( y, and z directions).  A smaller round plate is on the left side in x direction.  The right side is a rectangular plane either with or without a hole.  In testing studies, the KSP solver works fine both with and without -pc_type hypre runtime option for the domain with a whole plane(without a hole) on the right, but diverges for the case of a plane with a hole with -ps_type hypre option. 

  My question is whether the hypre pre-conditioner is sensitive to the geometry boundary?  If the answer is yes, is there any other pre-conditioner available for my particular case(the domain with a plane which with a hole on the right side) to reduce the number of iterations? Thanks in advance.

 		 	   		  
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