[petsc-users] Solving Poisson equation with multigrid

[Michele Rosso]

I run with

-pc_type gamg  -options_left

and I get the error:

[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[0]PETSC ERROR: No support for this operation for this object type!
[0]PETSC ERROR: For coloring efficiency ensure number of grid points in 
X is divisible
                  by 2*stencil_width + 1
!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 3, Wed Aug 29 
11:26:24 CDT 2012
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: ./hit on a  named nid22318 by Unknown Fri May 17 
19:21:25 2013
[0]PETSC ERROR: Libraries linked from
[0]PETSC ERROR: Configure run at
[0]PETSC ERROR: Configure options
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: DMCreateColoring_DA_3d_MPIAIJ() line 288 in 
src/dm/impls/da/fdda.c
[0]PETSC ERROR: DMCreateColoring_DA() line 172 in src/dm/impls/da/fdda.c
[0]PETSC ERROR: DMCreateColoring() line 709 in src/dm/interface/dm.c
[0]PETSC ERROR: DMComputeJacobian() line 2206 in src/dm/interface/dm.c
[0]PETSC ERROR: KSPSetUp() line 228 in src/ksp/ksp/interface/itfunc.c


The code is calling

KSPSetFromOptions()


On 05/17/2013 05:10 PM, Jed Brown wrote:
> Please always use "reply-all" so that your messages go to the list.
> This is standard mailing list etiquette.  It is important to preserve
> threading for people who find this discussion later and so that we do
> not waste our time re-answering the same questions that have already
> been answered in private side-conversations.  You'll likely get an
> answer faster that way too.
>
> Michele Rosso <mrosso at uci.edu> writes:
>
>> If you are referring to -pc_type gamg, I tried it, but I got the same
>> error message
>> (For coloring efficiency ensure number of grid points in X is divisible
>> by 2*stencil_width + 1)
> The option could not have been used.  Always send the ENTIRE error
> message.  Is the code calling KSPSetFromOptions()?  Run with
> -options_left to see if any options did not get used.
>
>> On 05/17/2013 04:49 PM, Jed Brown wrote:
>>> Read my first message
>>>
>>> On May 17, 2013 6:47 PM, "Michele Rosso" <mrosso at uci.edu
>>> <mailto:mrosso at uci.edu>> wrote:
>>>
>>>      Ok, I will give a try to AMG then. What is it exactly?
>>>      Thank you!
>>>
>>>      On 05/17/2013 04:25 PM, Jed Brown wrote:
>>>>      Michele Rosso<mrosso at uci.edu>  <mailto:mrosso at uci.edu>  writes:
>>>>
>>>>>      So should I always use an odd number of grid points?
>>>>>      There is no way around this?
>>>>      If you want to use regular geometric coarsening, then yes.  That *is*
>>>>      regular node-centered coarsening.  Just consider the base case of one
>>>>      element:
>>>>
>>>>
>>>>         o ------- o
>>>>
>>>>      Split that in two:
>>>>
>>>>         o -- o -- o
>>>>
>>>>      Look, an odd number of vertices, and as we keep refining, it will stay
>>>>      odd.
>>>>
>>>>      You can use AMG or write your own interpolation if you want irregular coarsening.
>>>>

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