<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Mon, Mar 19, 2018 at 5:19 AM, TAY wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</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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<div class="m_4970404346621557354moz-cite-prefix">On 17/3/2018 1:15 AM, Matthew Knepley
wrote:<br>
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<div class="gmail_quote">On Fri, Mar 16, 2018 at 12:54 PM, TAY
wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
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<div class="m_4970404346621557354gmail-m_-1748057115269175174moz-cite-prefix">On
15/3/2018 6:21 PM, Matthew Knepley wrote:<br>
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<div class="gmail_quote">On Thu, Mar 15, 2018 at
3:51 PM, TAY wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
I'm running a CFD code which solves the
momentum and Poisson eqns.<br>
<br>
Due to poor scaling with HYPRE at higher cpu
no., I decided to try using PETSc with
boomeramg and gamg.<br>
<br>
I tested for some small cases and it work
well. However, for the large problem which has
poor scaling, it gives an error when I change
my Poisson solver from pure HYPRE to PETSc
with boomeramg and gamg.<br>
<br>
The error is :<br>
<br>
Caught signal number 11 SEGV: Segmentation
Violation, probably memory access out of range<br>
<br>
I tried using:<br>
<br>
-poisson_ksp_type richardson -poisson_pc_type
hypre -poisson_pc_type_hypre boomeramg<br>
<br>
-poisson_ksp_type gmres -poisson_pc_type hypre
-poisson_pc_type_hypre boomeramg<br>
<br>
-poisson_pc_type gamg
-poisson_pc_gamg_agg_nsmooths 1<br>
<br>
but they all gave similar error.<br>
<br>
So why is this so? How should I troubleshoot?
I am now running a debug ver of PETSc to check
the error msg.</blockquote>
<div><br>
</div>
<div>1) For anything like this, we would like to
see a stack trace from the debugger or
valgrind output.</div>
<div><br>
</div>
<div>2) We do have several Poisson examples.
Does it fail for you on those?</div>
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Hi,<br>
<br>
Can you recommend me some suitable egs? Esp in Fortran?<br>
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<div><br>
</div>
<div>Here is 2D Poisson</div>
<div><br>
</div>
<div> <a href="https://bitbucket.org/petsc/petsc/src/4b6141395f14f0c7d1415a2ff0158eec75a27d63/src/snes/examples/tutorials/ex5f.F90?at=master&fileviewer=file-view-default" target="_blank">https://bitbucket.org/petsc/<wbr>petsc/src/<wbr>4b6141395f14f0c7d1415a2ff0158e<wbr>ec75a27d63/src/snes/examples/<wbr>tutorials/ex5f.F90?at=master&<wbr>fileviewer=file-view-default</a></div>
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<div>3) You can also try ML, which is the same
type of MG as GAMG. (--download-ml).</div>
<div><br>
</div>
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I have recompiled PETSc with ML. Is there an example command line
options which I can use for ML?<br></div></blockquote><div><br></div><div>-pc_type ml</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div text="#000000" bgcolor="#FFFFFF">
Another question is generally speaking, is geometric multigrid (GMG)
faster than algebraic?<br></div></blockquote><div><br></div><div>No, only for the setup time.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div text="#000000" bgcolor="#FFFFFF">
I tested on a small problem and the time taken varies from 1.15min
(HYPRE, geometric) to 3.25 (GAMG). BoomerAMG is 1.45min.<br></div></blockquote><div><br></div><div>I am not sure what you are running when you say Hypre geometric.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div text="#000000" bgcolor="#FFFFFF">
Besides HYPRE, is there any other GMG I can use? <br></div></blockquote><div><br></div><div>As I said above, it does not converge any faster and the solve is not faster, its all setup time, so small problems will look faster.</div><div>You should be doing 10-20 iterates. If you are doing more, MG is not working.<br></div><div><br></div><div>If you truly have a structured grid, then use DMDA in PETSc and you can use GMG with</div><div><br></div><div> -pc_type mg -pc_mg_nlevels <n></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 text="#000000" bgcolor="#FFFFFF">
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My cluster can't connect to the internet. Where can I
1st download it?<br>
<br>
Similarly, how can I find out the location of the ext
software by myself?<br>
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<div><br>
</div>
<div>The locations are all in the configure Python modules:</div>
<div><br>
</div>
<div> <a href="https://bitbucket.org/petsc/petsc/src/4b6141395f14f0c7d1415a2ff0158eec75a27d63/config/BuildSystem/config/packages/ml.py?at=master&fileviewer=file-view-default" target="_blank">https://bitbucket.org/petsc/<wbr>petsc/src/<wbr>4b6141395f14f0c7d1415a2ff0158e<wbr>ec75a27d63/config/BuildSystem/<wbr>config/packages/ml.py?at=<wbr>master&fileviewer=file-view-<wbr>default</a></div>
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<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
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<div> Thanks,</div>
<div><br>
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<div> Matt</div>
<div> </div>
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-- <br>
Thank you very much.<br>
<br>
Yours sincerely,<br>
<br>
==============================<wbr>==================<br>
TAY Wee-Beng (Zheng Weiming) 郑伟明<br>
Personal research webpage: <a href="http://tayweebeng.wixsite.com/website" rel="noreferrer" target="_blank">http://tayweebeng.wixsite.com/<wbr>website</a><br>
Youtube research showcase: <a href="https://www.youtube.com/channel/UC72ZHtvQNMpNs2uRTSToiLA" rel="noreferrer" target="_blank">https://www.youtube.com/channe<wbr>l/UC72ZHtvQNMpNs2uRTSToiLA</a><br>
linkedin: <a href="http://www.linkedin.com/in/tay-weebeng" rel="noreferrer" target="_blank">www.linkedin.com/in/tay-weeben<wbr>g</a><br>
==============================<wbr>==================<br>
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<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>
<div><br>
</div>
<div><a href="http://www.caam.rice.edu/%7Emk51/" target="_blank">https://www.cse.buffalo.edu/~k<wbr>nepley/</a><br>
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-- <br>
<div class="m_4970404346621557354gmail_signature">
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<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>
<div><br>
</div>
<div><a href="http://www.caam.rice.edu/%7Emk51/" target="_blank">https://www.cse.buffalo.edu/~<wbr>knepley/</a><br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><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><div><br></div><div><a href="http://www.caam.rice.edu/~mk51/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div>
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