<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Thu, Jan 23, 2014 at 9:02 AM, Dave May <span dir="ltr"><<a href="mailto:dave.mayhem23@gmail.com" target="_blank">dave.mayhem23@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div>It should be just "est".<br>
</div></div></blockquote><div><br></div><div>I cannot explain</div><div><br></div><div> <a href="https://bitbucket.org/petsc/petsc/src/82b87d87c781ccd50dbcf95f010f70771da1bbfc/src/ksp/ksp/impls/specest/specest.c?at=master#cl-130">https://bitbucket.org/petsc/petsc/src/82b87d87c781ccd50dbcf95f010f70771da1bbfc/src/ksp/ksp/impls/specest/specest.c?at=master#cl-130</a></div>
<div><br></div><div>or</div><div><br></div><div> <a href="https://bitbucket.org/petsc/petsc/src/82b87d87c781ccd50dbcf95f010f70771da1bbfc/src/ksp/ksp/impls/specest/specest.c?at=master#cl-175">https://bitbucket.org/petsc/petsc/src/82b87d87c781ccd50dbcf95f010f70771da1bbfc/src/ksp/ksp/impls/specest/specest.c?at=master#cl-175</a></div>
<div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr">
<div></div>However, I misspelled "cheby". Those options should be<br><br>-mg_levels_ksp_type chebyshev<br>-mg_levels_ksp_chebyshev_estimate_eigenvalues 0,0.2,0,1.1<br>
<br><br><br><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On 23 January 2014 15:56, 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:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">
<div>On Thu, Jan 23, 2014 at 8:54 AM, Dave May <span dir="ltr"><<a href="mailto:dave.mayhem23@gmail.com" target="_blank">dave.mayhem23@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><div>If you don't have any prefix set on the outer KSP, you should be able to simply do<br>
<br>
-mg_levels_ksp_type chebychev<br>-mg_levels_ksp_chebychev_estimate_eigenvalues 0,0.2,0,1.1<br>-mg_levels_est_ksp_type cg<br>
-mg_levels_est_ksp_max_it X<br></div></div></div></blockquote><div><br></div></div><div>Are you sure the est_ is not specest_?</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div><div>
<div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div dir="ltr"><div><div></div>Cheers,<br></div> Dave<br><div><div><br><br><br></div></div></div><div><div><div class="gmail_extra"><br><br><div class="gmail_quote">On 23 January 2014 15:49, 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:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div>On 2014-01-23 14:32, Matthew Knepley wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
On Thu, Jan 23, 2014 at 5:35 AM, Garth N. Wells <<a href="mailto:gnw20@cam.ac.uk" target="_blank">gnw20@cam.ac.uk</a>><br>
wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Is there are command line option to set the number of iterations<br>
used for the eigenvalue estimation inside the Chebyshev<br>
preconditioner? "-gamg_est_ksp_max_it" does the trick with GAMG,<br>
but I'd also like to change the number of iterations when using<br>
Chebyshev smoothing with ML.<br>
</blockquote>
<br>
In GAMG, we use PETSc itself to do the estimate, and give it the<br>
prefix gamg_est_. In ML, as far as I can see from the code, we use the<br>
internal<br>
estimator, and I don't think they give us this knob.<br>
<br>
</blockquote>
<br></div>
I'm not so interested in the what happens inside ML, but the Chebyshev smoother that PETSc applies. With the default 10 GMRES iterations, the eigenvalue estimate is not good enough for my problem, which leads to the outer CG breaking down with an indefinite operator error.<br>
<br>
I can get it working by changing<br>
<br>
-mg_levels_ksp_chebyshev_<u></u>estimate_eigenvalues<br>
<br>
but I'd rather do a few more iterations to get a better eigenvalue estimate. It would also be nice to be able to switch from GMRES to CG. I can do this with GAMG via "-gamg_est_ksp_type"<span><font color="#888888"><br>
<br>
Garth</font></span><div><div><br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Matt<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Garth<br>
</blockquote>
<br><span class=""><font color="#888888">
--<br>
What most experimenters take for granted before they begin their<br>
experiments is infinitely more interesting than any results to which<br>
their experiments lead.<br>
-- Norbert Wiener<br>
</font></span></blockquote><span class=""><font color="#888888">
</font></span></div></div></blockquote></div><span class=""><font color="#888888"><br></font></span></div><span class=""><font color="#888888">
</font></span></div></div></blockquote></div></div></div><span class=""><font color="#888888"><div><div><br><br clear="all"><div><br></div>-- <br>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></font></span></div></div>
</blockquote></div><br></div>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>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>