[Trilinos-Users] IFPACK preconditioners reordering

[Erik Boman]

Danielle,

In general RCM has been found to be the best ordering for incomplete 
factorizations, so other orderings may not help you.
Still, to clarify the status in Trilinos:

- Ifpack supports both RCM and Metis (directly without Zoltan, possibly 
only older versions) so you could try nested dissection easily that way.
- Ifpack ordering only works in parallel as it is embedded within 
Additive Schwarz (known bug).
- Isorropia can compute orderings using Zoltan but not sure how to pass 
that to Ifpack. (I have never done it.)
- Going forward, Ifpack2 will use Zoltan2 for reordering and adding more 
orderings to Zoltan2 is work in progress.

Hope this helps.

Erik

On 02/18/2016 01:08 PM, Heroux, Michael A wrote:
> Danielle,
>
> Ifpack supports only Reverse Cuthill-McKee (RCM) and Metis reorderings.
>
> The Isorropia package provides an Epetra interface to Zoltan, and does 
> have orderings based on ParMetis and PT-Scotch, but I don’t know of a 
> way to get the orderings to work the Ifpack.  Perhaps one of the 
> Isorropia developers could confirm.
>
> Mike
>
> From: Trilinos-Users <trilinos-users-bounces at trilinos.org 
> <mailto:trilinos-users-bounces at trilinos.org>> on behalf of Danielle 
> Catherine Maddix <dcmaddix at stanford.edu <mailto:dcmaddix at stanford.edu>>
> Date: Wednesday, February 17, 2016 at 7:24 PM
> To: Trilinos Users <trilinos-users at trilinos.org 
> <mailto:trilinos-users at trilinos.org>>
> Subject: [EXTERNAL] [Trilinos-Users] IFPACK preconditioners reordering
>
> Hello,
>
>
> I was using the IFPACK pre conditioners, with particular interest in 
> IC. I was wondering if there were any built-in Trilinos reordering 
> schemes that could be done for banding on my matrix in the 
> preconditioner calculation.  I know that ILUT and ILUt uses RCM by 
> default. Are there other reordering options, such as nested 
> dissection, which uses Zoltan?
>
>
> Thank you,
>
> Danielle Maddix
>
>
>
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