<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12pt"><div>I do not explicitily check the size, because I use <span style="font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px;">PETSC_DECIDE, instead I specify the number of processes. What I really care about is hw does KSPSolve solve the system in a parallel way with multiple processes.</span></div><div class="yahoo_quoted" style="display: block;"> <br> <br> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div dir="ltr"> <font size="2" face="Arial"> Il Mercoledì 8 Gennaio 2014 12:34, Dave May <dave.mayhem23@gmail.com> ha scritto:<br>
</font> </div> <div class="y_msg_container"><div id="yiv5062395357"><div><div dir="ltr"><div><div><div><div><div><div>Please check out the manual page for MatSetSizes()<br clear="none"> <a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetSizes.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatSetSizes.html</a><br clear="none">
<br clear="none"></div>Basically you have two choices:<br clear="none"></div><br clear="none">1/ Define the global size of the matrix and use PETSC_DECIDE for the local sizes.<br clear="none"></div>In this case, PETSc will define the local row size in a manner such that there are approximately the same number of rows on each process.<br clear="none">
</div><br clear="none">2/ Define the local sizes yourself and use PETSC_DETERMINE for the global size. <br clear="none">Then you have full control over the parallel layout.<br clear="none"><br clear="none"></div>The following functions described by these pages<br clear="none"><br clear="none"> <a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetSize.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetSize.html</a><br clear="none">
<a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSize.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSize.html</a><br clear="none"> <a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRanges.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRanges.html</a><br clear="none">
</div> <a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRangesColumn.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRangesColumn.html</a><br clear="none"><br clear="none">
might also be useful for you in double checking what the matrix decomposition looks like<br clear="none"><div><div><br clear="none"><div><div><div><div><br clear="none"></div><div>Cheers,<br clear="none"></div><div> Dave<br clear="none"></div><div><br clear="none"></div></div></div></div></div></div>
</div><div class="yiv5062395357yqt7598806752" id="yiv5062395357yqt39511"><div class="yiv5062395357gmail_extra"><br clear="none"><br clear="none"><div class="yiv5062395357gmail_quote">On 8 January 2014 12:26, mary sweat <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:mary.sweat78@yahoo.it" target="_blank" href="mailto:mary.sweat78@yahoo.it">mary.sweat78@yahoo.it</a>></span> wrote:<br clear="none">
<blockquote class="yiv5062395357gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div style="font-size: 12pt; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif;"><div>
My target is the following. I got a huge linear system with a sparse huge matrix, nothing to deal with PDE. How is the system splitted between processes? is there in this suggested book the answer?</div><div>Thanks again</div>
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<div dir="ltr"> <font face="Arial"> Il Martedì 7 Gennaio 2014 17:34, Jed Brown <<a rel="nofollow" shape="rect" ymailto="mailto:jedbrown@mcs.anl.gov" target="_blank" href="mailto:jedbrown@mcs.anl.gov">jedbrown@mcs.anl.gov</a>> ha scritto:<br clear="none"> </font> </div><div><div class="yiv5062395357h5"> <div>
mary sweat <<a rel="nofollow" shape="rect" ymailto="mailto:mary.sweat78@yahoo.it" target="_blank" href="mailto:mary.sweat78@yahoo.it">mary.sweat78@yahoo.it</a>> writes:<div><br clear="none"><br clear="none">> Hi all, I need to know how does KSP separate and distribute domain<br clear="none">
> between processes and the way processes share and communicate halfway<br clear="none">> results. Is there any good documentation about it???</div><br clear="none"><br clear="none">The communication is in Mat and Vec functions. You can see it<br clear="none">
summarized in -log_summary. For the underlying theory, see Barry's<br clear="none">book.<br clear="none"><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www.mcs.anl.gov/~bsmith/ddbook.html">http://www.mcs.anl.gov/~bsmith/ddbook.html</a><br clear="none">
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