<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Fri, Jan 22, 2016 at 11:10 AM, Hom Nath Gharti <span dir="ltr"><<a href="mailto:hng.email@gmail.com" target="_blank">hng.email@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Thanks Matt.<br>
<br>
Attached detailed info on ksp of a much smaller test. This is a<br>
multiphysics problem.<br></blockquote><div><br></div><div>You are using FGMRES/ASM(ILU0). From your description below, this sounds like</div><div>an elliptic system. I would at least try AMG (-pc_type gamg) to see how it does. Any</div><div>other advice would have to be based on seeing the equations.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hom Nath<br>
<br>
On Fri, Jan 22, 2016 at 12:01 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>> wrote:<br>
> On Fri, Jan 22, 2016 at 10:52 AM, Hom Nath Gharti <<a href="mailto:hng.email@gmail.com">hng.email@gmail.com</a>><br>
> wrote:<br>
>><br>
>> Dear all,<br>
>><br>
>> I take this opportunity to ask for your important suggestion.<br>
>><br>
>> I am solving an elastic-acoustic-gravity equation on the planet. I<br>
>> have displacement vector (ux,uy,uz) in solid region, displacement<br>
>> potential (\xi) and pressure (p) in fluid region, and gravitational<br>
>> potential (\phi) in all of space. All these variables are coupled.<br>
>><br>
>> Currently, I am using MATMPIAIJ and form a single global matrix. Does<br>
>> using a MATMPIBIJ or MATNEST improve the convergence/efficiency in<br>
>> this case? For your information, total degrees of freedoms are about a<br>
>> billion.<br>
><br>
><br>
> 1) For any solver question, we need to see the output of -ksp_view, and we<br>
> would also like<br>
><br>
> -ksp_monitor_true_residual -ksp_converged_reason<br>
><br>
> 2) MATNEST does not affect convergence, and MATMPIBAIJ only in the blocksize<br>
> which you<br>
> could set without that format<br>
><br>
> 3) However, you might see benefit from using something like PCFIELDSPLIT if<br>
> you have multiphysics here<br>
><br>
> Matt<br>
><br>
>><br>
>> Any suggestion would be greatly appreciated.<br>
>><br>
>> Thanks,<br>
>> Hom Nath<br>
>><br>
>> On Fri, Jan 22, 2016 at 10:32 AM, Matthew Knepley <<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>><br>
>> wrote:<br>
>> > On Fri, Jan 22, 2016 at 9:27 AM, Mark Adams <<a href="mailto:mfadams@lbl.gov">mfadams@lbl.gov</a>> wrote:<br>
>> >>><br>
>> >>><br>
>> >>><br>
>> >>> I said the Hypre setup cost is not scalable,<br>
>> >><br>
>> >><br>
>> >> I'd be a little careful here. Scaling for the matrix triple product is<br>
>> >> hard and hypre does put effort into scaling. I don't have any data<br>
>> >> however.<br>
>> >> Do you?<br>
>> ><br>
>> ><br>
>> > I used it for PyLith and saw this. I did not think any AMG had scalable<br>
>> > setup time.<br>
>> ><br>
>> > Matt<br>
>> ><br>
>> >>><br>
>> >>> but it can be amortized over the iterations. You can quantify this<br>
>> >>> just by looking at the PCSetUp time as your increase the number of<br>
>> >>> processes. I don't think they have a good<br>
>> >>> model for the memory usage, and if they do, I do not know what it is.<br>
>> >>> However, generally Hypre takes more<br>
>> >>> memory than the agglomeration MG like ML or GAMG.<br>
>> >>><br>
>> >><br>
>> >> agglomerations methods tend to have lower "grid complexity", that is<br>
>> >> smaller coarse grids, than classic AMG like in hypre. THis is more of a<br>
>> >> constant complexity and not a scaling issue though. You can address<br>
>> >> this<br>
>> >> with parameters to some extent. But for elasticity, you want to at<br>
>> >> least<br>
>> >> try, if not start with, GAMG or ML.<br>
>> >><br>
>> >>><br>
>> >>> Thanks,<br>
>> >>><br>
>> >>> Matt<br>
>> >>><br>
>> >>>><br>
>> >>>><br>
>> >>>> Giang<br>
>> >>>><br>
>> >>>> On Mon, Jan 18, 2016 at 5:25 PM, Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:<br>
>> >>>>><br>
>> >>>>> Hoang Giang Bui <<a href="mailto:hgbk2008@gmail.com">hgbk2008@gmail.com</a>> writes:<br>
>> >>>>><br>
>> >>>>> > Why P2/P2 is not for co-located discretization?<br>
>> >>>>><br>
>> >>>>> Matt typed "P2/P2" when me meant "P2/P1".<br>
>> >>>><br>
>> >>>><br>
>> >>><br>
>> >>><br>
>> >>><br>
>> >>> --<br>
>> >>> What most experimenters take for granted before they begin their<br>
>> >>> experiments is infinitely more interesting than any results to which<br>
>> >>> their<br>
>> >>> experiments lead.<br>
>> >>> -- Norbert Wiener<br>
>> >><br>
>> >><br>
>> ><br>
>> ><br>
>> ><br>
>> > --<br>
>> > What most experimenters take for granted before they begin their<br>
>> > experiments<br>
>> > is infinitely more interesting than any results to which their<br>
>> > experiments<br>
>> > lead.<br>
>> > -- Norbert Wiener<br>
><br>
><br>
><br>
<span class="HOEnZb"><font color="#888888">><br>
> --<br>
> What most experimenters take for granted before they begin their experiments<br>
> is infinitely more interesting than any results to which their experiments<br>
> lead.<br>
> -- Norbert Wiener<br>
</font></span></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener</div>
</div></div>