[petsc-users] Why use MATMPIBAIJ?

[Hom Nath Gharti]

Dear all,

I take this opportunity to ask for your important suggestion.

I am solving an elastic-acoustic-gravity equation on the planet. I
have displacement vector (ux,uy,uz) in solid region, displacement
potential (\xi) and pressure (p) in fluid region, and gravitational
potential (\phi) in all of space. All these variables are coupled.

Currently, I am using MATMPIAIJ and form a single global matrix. Does
using a MATMPIBIJ or MATNEST improve the convergence/efficiency in
this case? For your information, total degrees of freedoms are about a
billion.

Any suggestion would be greatly appreciated.

Thanks,
Hom Nath

On Fri, Jan 22, 2016 at 10:32 AM, Matthew Knepley <knepley at gmail.com> wrote:
> On Fri, Jan 22, 2016 at 9:27 AM, Mark Adams <mfadams at lbl.gov> wrote:
>>>
>>>
>>>
>>> I said the Hypre setup cost is not scalable,
>>
>>
>> I'd be a little careful here.  Scaling for the matrix triple product is
>> hard and hypre does put effort into scaling. I don't have any data however.
>> Do you?
>
>
> I used it for PyLith and saw this. I did not think any AMG had scalable
> setup time.
>
>    Matt
>
>>>
>>> but it can be amortized over the iterations. You can quantify this
>>> just by looking at the PCSetUp time as your increase the number of
>>> processes. I don't think they have a good
>>> model for the memory usage, and if they do, I do not know what it is.
>>> However, generally Hypre takes more
>>> memory than the agglomeration MG like ML or GAMG.
>>>
>>
>> agglomerations methods tend to have lower "grid complexity", that is
>> smaller coarse grids, than classic AMG like in hypre. THis is more of a
>> constant complexity and not a scaling issue though.  You can address this
>> with parameters to some extent. But for elasticity, you want to at least
>> try, if not start with, GAMG or ML.
>>
>>>
>>>   Thanks,
>>>
>>>     Matt
>>>
>>>>
>>>>
>>>> Giang
>>>>
>>>> On Mon, Jan 18, 2016 at 5:25 PM, Jed Brown <jed at jedbrown.org> wrote:
>>>>>
>>>>> Hoang Giang Bui <hgbk2008 at gmail.com> writes:
>>>>>
>>>>> > Why P2/P2 is not for co-located discretization?
>>>>>
>>>>> Matt typed "P2/P2" when me meant "P2/P1".
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> What most experimenters take for granted before they begin their
>>> experiments is infinitely more interesting than any results to which their
>>> experiments lead.
>>> -- Norbert Wiener
>>
>>
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener