<div dir="ltr">FYI, ML has some different defaults (eg, its "threshold" is 0 and GAMG is finite as I recall). I have "verified" GAMG against ML a year or so ago, but I had to set: -pc_gamg_threshold 0.<div>Mark</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jun 12, 2015 at 7:38 AM, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><div class="h5">On Fri, Jun 12, 2015 at 6:24 AM, Garth N. Wells <span dir="ltr"><<a href="mailto:gnw20@cam.ac.uk" target="_blank">gnw20@cam.ac.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I've noticed very different performance with ML when I (a) link PETSc<br>
to a Trilinos installation; or (b) use --download-ml. I observe<br>
<br>
- Case (a): solver behaves exactly as I would expect. Iteration counts<br>
very close to GAMG iteration counts, minimal dependency on problem<br>
size.<br>
<br>
- Case (b): iteration counts higher and substantial increase in<br>
iteration count with problem size.<br>
<br>
I haven't debugged since I usually link to Trilinos, in which case<br>
performance is as I expect.</blockquote><div><br></div></div></div><div>ML stopped being distributed independent of Trilinos a while ago, so we might not</div><div>have upstream changes. This sounds like a difference of settings. The first step I think</div><div>is to look at -ksp_view for both runs.</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"><span><font color="#888888">
Garth<span class="HOEnZb"><font color="#888888"><br>
</font></span></font></span></blockquote></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div>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>
</font></span></div></div>
</blockquote></div><br></div>