[petsc-users] Recommended solver and preconditioner to solve Poisson eqn on win7

[Jed Brown]

Also, add -pc_gamg_agg_nsmooths 1 as Mark suggested. It will reduce the
iteration count significantly at the expense of somewhat higher setup cost.

On Fri, Sep 14, 2012 at 6:11 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> *
> *
> *      ##########################################################*
> *      #                                                        #*
> *      #                          WARNING!!!                    #*
> *      #                                                        #*
> *      #   This code was compiled with a debugging option,      #*
> *      #   To get timing results run ./configure                #*
> *      #   using --with-debugging=no, the performance will      #*
> *      #   be generally two or three times faster.              #*
> *      #                                                        #*
> *      ##########################################################*
>
> On Fri, Sep 14, 2012 at 6:08 PM, Zhenglun (Alan) Wei <
> zhenglun.wei at gmail.com> wrote:
>
>>  I'm sorry about that. I attached the output files here with '
>> -ksp_monitor -ksp_view -log_summary'. They are named after the grid size
>> and pc-type.
>>
>> cheers,
>> Alan
>>
>> On 9/14/2012 5:51 PM, Jed Brown wrote:
>>
>> On Fri, Sep 14, 2012 at 5:49 PM, Matthew Knepley <knepley at gmail.com>wrote:
>>
>>> On Fri, Sep 14, 2012 at 5:40 PM, Zhenglun (Alan) Wei <
>>> zhenglun.wei at gmail.com> wrote:
>>>
>>>>  Dear folks,
>>>>     I did some test with -pc_type gamg with
>>>> /src/ksp/ksp/example/tutorial/ex45.c. It is not as good as default -pc_type
>>>> when my mesh (Cartisian) is 100*50*50; while it is a little bit better than
>>>> the default one when the mesh is 200*100*100. Therefore, I guess this type
>>>> of pc is good for larger problem. Is that ture? or is there any rule of
>>>> thumb for this type of preconditioner? BTW, I tested it with 8 processes.
>>>>
>>>
>>>  When asking questions about convergence, always always ALWAYS send the
>>> output of -ksp_monitor -ksp_view. If
>>> you don't, we are just guessing blindly.
>>>
>>
>>  And -log_summary because this is about performance.
>>
>>
>>
>
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