On Mon, Mar 14, 2011 at 3:17 PM, Travis Austin <span dir="ltr"><<a href="mailto:austin@txcorp.com">austin@txcorp.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="word-wrap:break-word"><div>Hi,</div><div><br></div><div>Often for high-order finite elements the subdomains in an additive Schwarz method (using PCASM) are defined according to the elements</div><div>since they can contain a large number of degrees of freedom. This is an approach used extensively by Paul Fischer of Argonne National</div>
<div>Lab in his work. I'm trying to code this up for an example that I have using high-order finite elements but I'm running into a few issues. </div><div><br></div><div>Below is a trivial partitioning of a 1D problem that illustrates what I am trying to overcome. Processor P0 is going to have 3 ASM subdomains</div>
<div>and each subdomain will fully be on the processor. However, processor P1 with 4 ASM subdomains will have one subdomain that is partly on</div><div>processor P0. </div><div><br></div><div>Is there a way that I can define the local subdomain in the ASM preconditioning for processor P1 corresponding to the middle most element so </div>
<div>that the ASM preconditioning part for this element is performed on processor P1?</div><div><br></div><div>Can I define an index set for processor P1 that includes the degree of freedom from the P0/P1 interface and expect that PETSc will handle</div>
<div>that? </div></div></blockquote><div><br></div><div>You can define the block explicitly for ASM,</div><div><br></div><div> <a href="http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/PC/PCASMSetLocalSubdomains.html">http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/PC/PCASMSetLocalSubdomains.html</a></div>
<div><br></div><div>If you want a single block per process, you can use PETSC_NULL for islocal and only define the overlapping blocks.</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;">
<div style="word-wrap:break-word"><div> P0</div><div> </div><div> / ---------------------------------------\ </div><div><br></div><div> | | | | | | | |</div>
<div> |---x---x---X---x---x---X---x---x---X---x---x---X---x---x---X---x---x---X---x---x---|</div><div> | | | | | | | |</div>
<div><br></div><div> \--------------------------------------------------/</div><div> </div><div> P1</div>
<div><br></div><div>Thanks,</div><div>Travis Austin</div><div><br><div>
<span style="border-collapse:separate;border-spacing:0px 0px;color:rgb(0, 0, 0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="border-collapse:separate;border-spacing:0px 0px;color:rgb(0, 0, 0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^</div><div>Travis Austin, Ph.D.</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">Tech-X Corporation</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">
5621 Arapahoe Ave, Suite A</div><div style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px">Boulder, CO 80303</div><div><a href="mailto:austin@txcorp.com" target="_blank">austin@txcorp.com</a></div><div>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^</div><br></span></span>
</div>
<br><div><div>On Oct 6, 2010, at 11:36 AM, Jed Brown wrote:</div><br><blockquote type="cite"><div><a href="http://59A2.org/na/Brown-EfficientNonlinearSolversNodalHighOrder3D-2010.pdf" target="_blank">http://59A2.org/na/Brown-EfficientNonlinearSolversNodalHighOrder3D-2010.pdf</a><br>
</div></blockquote></div><br></div></div></blockquote></div><br><br clear="all"><br>-- <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<br>