[Trilinos-Users] [EXTERNAL] question about MueLu (AMG) setting

[Andrey Prokopenko]

Hi Hisanao,
> >Do you have coordinates available?
>
> Yes, I can use my physical coordinates data for repartitioning in my 
> simulation.
>
> In our 2D hydraulic fracturing simulation, each elements has four 
> unknowns (displacement of x and y, pore pressure, fracture fluid 
> pressure). At that case, if the number of elements is N, do I have to 
> provide the element positions of N elements?  In addition, how do I 
> give the information that each element has four unknowns.
What are the degrees of freedom of the matrix that you pass to MueLu? 
The coordinates should correspond to those. So, for instance, if the 
dofs are pressure, you should pass pressure coordinates. For instance, 
if your pressure is associated with a center of element, you should pass 
coordinates of the center.

> >Also, how do you construct MueLu preconditioner?
>
> I don't use Tpetra because I am using Aztecoo.
> I construct MueLu preconditioner by MueLu::EpetraOperator.
> In this case, how do I provide the coordinate information?
> Could you show me an example code to provide the physical coordinates?

If you are using Epetra, there is a similar function called 
CreateEpetraPreconditioner, which also takes coordinates as 3rd 
argument. This is the preferable way to construct the preconditioner. 
Otherwise, if I understand correctly what you mean, you first need to 
construct a MueLu hierarchy, and then construct MueLu::EpetraOperator. 
CreateEpetraPreconditioner, on the other hand, does that work for you.

-Andrey

On 07/10/2015 04:20 PM, Ouchi Hisanao wrote:
> Hi Andrey,
>
> >Do you have coordinates available?
>
> Yes, I can use my physical coordinates data for repartitioning in my 
> simulation.
>
> In our 2D hydraulic fracturing simulation, each elements has four 
> unknowns (displacement of x and y, pore pressure, fracture fluid 
> pressure). At that case, if the number of elements is N, do I have to 
> provide the element positions of N elements?  In addition, how do I 
> give the information that each element has four unknowns.
>
> >Also, how do you construct MueLu preconditioner?
>
> I don't use Tpetra because I am using Aztecoo.
> I construct MueLu preconditioner by MueLu::EpetraOperator.
> In this case, how do I provide the coordinate information?
> Could you show me an example code to provide the physical coordinates?
>
> Hisanao
>
>
>
>
>
>
> 2015-07-10 16:52 GMT-05:00 Andrey Prokopenko <aprokop at sandia.gov 
> <mailto:aprokop at sandia.gov>>:
>
>     Oh, I see. In order to use repartitioning at the moment you have
>     to provide the physical coordinates of nodes corresponding to
>     degrees of freedom of the matrix you pass to MueLu. We require
>     that information as we use geometric partitioning to do rebalancing.
>
>     Do you have coordinates available? Also, how do you construct
>     MueLu preconditioner? If it is through CreateTpetraPreconditioner,
>     you can simply pass these coordinates as a 3rd argument.
>
>     -Andrey
>
>
>     On 07/10/2015 03:46 PM, Ouchi Hisanao wrote:
>>     Hi Andrey,
>>
>>     Thank you very much for your reply.
>>
>>     According to your advice, I modified my input deck based on a new
>>     style (please see the bottom of my email) and simply add the
>>     following sentence as you suggested.
>>
>>     <Parameter name="repartition: enable" type="bool" value="true"/>
>>
>>     However, I could not execute my code successfully since the
>>     following error message appeared.
>>
>>     -------------- ---------------------------- error messeage
>>     -------------------------------------------
>>     terminate called after throwing an instance of
>>     'MueLu::Exceptions::RuntimeError'
>>     what():  CoordinatesTransferFactory::DeclareInput: (LevelID = 0)
>>     unable to find or generate requested data "Coordinates" with
>>     generating factory "null"
>>       during request for data "  Coordinates" on level 0 by factory
>>     CoordinatesTransferFactory
>>       during request for data "  Coordinates" on level 1 by factory
>>     RebalanceTransferFactory
>>       during request for data "  P" on level 1 by factory NoFactory
>>     -----------------------------------------------------------------------------------------------------------
>>
>>     This error message appears not only in my program in my Ubuntu
>>     but also in the sample code in the MueLu virtual machine image
>>     distributed by Sandia as a tutorial. In the case of the MueLu
>>     virtual machine image, I just added the following sentence in the
>>     simplest example input deck  (n1_easy.xml) and executed the
>>     simplest example problem in the MueLu tutorial (Laplace 2D 50x50).
>>
>>     <Parameter name="repartition: enable" type="bool" value="true"/>
>>
>>     Do you have any idea to resolve this error?
>>
>>     Best regards,
>>
>>     Hisanao
>>
>>     ----------------------------- modified input deck
>>     -------------------------------------
>>     <ParameterList name="MueLu">
>>
>>     <Parameter name="verbosity" type="string" value="high"/>
>>
>>     <Parameter name="max levels" type="int" value="10"/>
>>     <Parameter name="coarse: max size" type="int" value="10"/>
>>
>>     <Parameter name="multigrid algorithm" type="string" value="sa"/>
>>     <Parameter name="sa: damping factor"  type="double" value="1.0"/>
>>
>>     <!-- Smoothing -->
>>     <!-- Comment/uncomment different sections to try different
>>     smoothers -->
>>     <Parameter name="smoother: type" type="string" value="ILUT"/>
>>      <!-- Rebalancing -->
>>     <Parameter name="repartition: enable" type="bool" value="true"/>
>>
>>     <!-- Aggregation -->
>>     <Parameter name="aggregation: type" type="string" value="uncoupled"/>
>>     <Parameter name="aggregation: min agg size" type="int" value="4"/>
>>
>>     </ParameterList>
>>
>>
>>
>>
>>
>
>
>
>


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