<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Tue, Aug 2, 2016 at 2:25 AM, Klaij, Christiaan <span dir="ltr"><<a href="mailto:C.Klaij@marin.nl" target="_blank">C.Klaij@marin.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p>Thanks for your help! Going from individual blocks to a whole<br>
matrix makes perfect sense if the blocks are readily available or<br>
needed as fully functional matrices. Don't change that! Maybe add<br>
the opposite?<br>
<br>
I'm surprised it's broken though: on this mailing list several<br>
petsc developers have stated on several occasions (and not just<br>
to me) things like "you should never have a matnest", "you should<br>
have a mat then change the type at runtime", "snes ex70 is not<br>
the intended use" and so on.<br>
<br>
I fully appreciate the benefit of having a format-independent<br>
assembly and switching mat type from aij to nest depending on the<br>
preconditioner. And given the manual and the statements on this<br>
list, I thought this would be standard practice and therefore<br>
thoroughly tested. But now I get the impression it has never<br>
worked...<br></p></div></blockquote><div>Yes, that way has never worked. Nest is only a memory optimization, and with</div><div>implicit problems I am never running at the limit of memory (or I use more procs).</div><div>The people I know who needed it had explicitly coded it in rather than trying to</div><div>use it from options. It should not take long to get this fixed.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" style="font-size:12pt;color:#000000;background-color:#ffffff;font-family:Calibri,Arial,Helvetica,sans-serif"><p>
Chris<br>
<br>
<br>
> From: Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>><br>
> Sent: Tuesday, August 02, 2016 12:28 AM<br>
> To: Klaij, Christiaan<br>
> Cc: <a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>; Jed Brown<br>
> Subject: Re: [petsc-users] block matrix without MatCreateNest<br>
> <br>
> On Mon, Aug 1, 2016 at 9:36 AM, Klaij, Christiaan <<a href="mailto:C.Klaij@marin.nl" target="_blank">C.Klaij@marin.nl</a>> wrote:<br>
> <br>
> Matt,<br>
> <br>
> <br>
> 1) great!<br>
> <br>
> <br>
> 2) ??? that's precisely why I paste the output of "cat mattry.F90" in the emails, so you have a small example that produces the errors I mention. Now I'm also attaching it to this email.<br>
> <br>
> Okay, I have gone through it. You are correct that it is completely broken.<br>
> <br>
> The way that MatNest currently works is that it trys to use L2G mappings from individual blocks<br>
> and then builds a composite L2G map for the whole matrix. This is obviously incompatible with<br>
> the primary use case, and should be changed to break up the full L2G into one for each block.<br>
> <br>
> Jed, can you fix this? I am not sure I know enough about how Nest works.<br>
> <br>
> Matt<br>
> <br>
> Thanks,<br>
> <br>
> Chris</p>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="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>
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