<html><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><div><div class="AppleOriginalContents"><blockquote type="cite"><div><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 18px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p></o:p></div></div><div><div><div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;"><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Let me know if you need any more info, or if the code is incomprehensible or so<o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">(it’s long because I’ve copied a lot from redistribute.c)<o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Kind regards,<o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Carl-Johan<o:p></o:p></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div><div><div style="border-width: 1pt medium medium; border-style: solid none none; border-image: none; padding: 3pt 0cm 0cm; border-color: currentcolor;"><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><b>From:</b><span class="xapple-converted-space"> </span>Barry Smith <<a href="mailto:bsmith@petsc.dev" style="color: blue; text-decoration: underline;">bsmith@petsc.dev</a>><span class="xapple-converted-space"> </span><br><b>Sent:</b><span class="xapple-converted-space"> </span>Thursday, April 20, 2023 3:17 PM<br><b>To:</b><span class="xapple-converted-space"> </span>Carl-Johan Thore <<a href="mailto:carl-johan.thore@liu.se" style="color: blue; text-decoration: underline;">carl-johan.thore@liu.se</a>><br><b>Subject:</b><span class="xapple-converted-space"> </span>Re: [petsc-users] Fieldsplit with redistribute<o:p></o:p></div></div></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> Sure<o:p></o:p></div></div><div><div><p class="MsoNormal" style="margin: 0cm 0cm 12pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;"><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">On Apr 20, 2023, at 4:09 AM, Carl-Johan Thore <<a href="mailto:carl-johan.thore@liu.se" style="color: blue; text-decoration: underline;">carl-johan.thore@liu.se</a>> wrote:<o:p></o:p></div></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Hi Barry,<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">In the conversation below you mentioned that I could send code to you to take a look. I’ve written<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">up what I think is a minimally working example for this. It’s almost there in the sense of distributing<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">the correct number of indices to the ranks to match the reduced matrix, but it’s the wrong indices.<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Would it be okay if I sent you the code to have look?<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Kind regards,<o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Carl-Johan<span class="xapple-converted-space"> </span><o:p></o:p></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div style="border-width: 1pt medium medium; border-style: solid none none; border-image: none; padding: 3pt 0cm 0cm; border-color: currentcolor;"><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><b>From:</b><span class="xapple-converted-space"> </span>Barry Smith <<a href="mailto:bsmith@petsc.dev" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">bsmith@petsc.dev</span></a>><span class="xapple-converted-space"> </span><br><b>Sent:</b><span class="xapple-converted-space"> </span>Sunday, April 16, 2023 10:31 PM<br><b>To:</b><span class="xapple-converted-space"> </span>Carl-Johan Thore <<a href="mailto:carl-johan.thore@liu.se" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">carl-johan.thore@liu.se</span></a>><br><b>Cc:</b><span class="xapple-converted-space"> </span><a href="mailto:petsc-users@mcs.anl.gov" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">petsc-users@mcs.anl.gov</span></a><br><b>Subject:</b><span class="xapple-converted-space"> </span>Re: [petsc-users] Fieldsplit with redistribute<o:p></o:p></div></div></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> The manual page for ISEmbed is incomprehensible to me. Anyways no matter what, you need to know what degrees of freedom are removed by PCDistribute() in order to produce the reduced IS which is why I think you need information only available inside PCSetUp_Redistribute(). (Sorry it is PCSetUp_Redistribute() not PCApply_Redistribute())<o:p></o:p></div></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> Barry<o:p></o:p></div></div></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div><div><p class="MsoNormal" style="margin: 0cm 0cm 12pt; font-size: 11pt; font-family: Calibri, sans-serif;"><br><br><o:p></o:p></p></div></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;"><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">On Apr 16, 2023, at 3:36 PM, Carl-Johan Thore <<a href="mailto:carl-johan.thore@liu.se" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">carl-johan.thore@liu.se</span></a>> wrote:<o:p></o:p></div></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div><div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Thanks for the quick reply Barry!<br>I have not tried the version with PCApply_Redistribute that you suggest, but I have a code that does roughly what you describe. It works when running on one rank, but fails on multiple ranks. I suspect the issue is with the use of ISEmbed as, quoting the PETSc-manual, "the resulting IS is sequential, since the index substitution it encodes is purely local" (admittedly I don't fully understand what that means). If you think using ISEmbed is not a good idea, I'll try PCApply_Redistribute()<o:p></o:p></div></div></div><div class="MsoNormal" align="center" style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif; text-align: center;"><hr size="2" width="98%" align="center"></div><div id="x_divRplyFwdMsg"><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><b>From:</b><span class="xapple-converted-space"> </span>Barry Smith <<a href="mailto:bsmith@petsc.dev" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">bsmith@petsc.dev</span></a>><br><b>Sent:</b><span class="xapple-converted-space"> </span>16 April 2023 21:11:18<br><b>To:</b><span class="xapple-converted-space"> </span>Carl-Johan Thore <<a href="mailto:carl-johan.thore@liu.se" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">carl-johan.thore@liu.se</span></a>><br><b>Cc:</b><span class="xapple-converted-space"> </span><a href="mailto:petsc-users@mcs.anl.gov" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">petsc-users@mcs.anl.gov</span></a><span class="xapple-converted-space"> </span><<a href="mailto:petsc-users@mcs.anl.gov" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">petsc-users@mcs.anl.gov</span></a>><br><b>Subject:</b><span class="xapple-converted-space"> </span>Re: [petsc-users] Fieldsplit with redistribute<span class="xapple-converted-space"> </span><o:p></o:p></div></div></div><div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div></div></div><div><div><p class="xmsonormal" style="margin-right: 0cm; margin-left: 0cm; font-size: 11pt; font-family: Calibri, sans-serif; margin-bottom: 12pt;"><br> There is no code to do this currently.<span class="xapple-converted-space"> </span><br><br> I would start by building your IS for each split before the PCRedistribute and then adding to the PCApply_Redistribute() code that "fixes" these IS by "removing" the entries of the IS associated with removed degrees of freedom and then shifting the entries indices of the IS by taking into account the removed indices. But you have probably already been trying this? It does require digging directly into the PCApply_Redistribute() to get the needed information (which degrees of freedom are removed by the redistribute code), plus it requires shifting the MPI rank ownership of the entries of the IS in the same way the MPI rank ownership of the degrees of freedom of the vector are moved.<br><br> If you have some code that you think should be doing this but doesn't work feel free to send it to us and we may be able to fix it.<br><br> Barry<br><br><br>> On Apr 16, 2023, at 2:50 PM, Carl-Johan Thore via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" style="color: blue; text-decoration: underline;"><span style="color: rgb(5, 99, 193);">petsc-users@mcs.anl.gov</span></a>> wrote:<br>><span class="xapple-converted-space"> </span><br>> Hello,<br>> I'm solving a blocksystem<br>> [A C;<br>> C' D],<br>> where D is not zero, using the PCFIELDSPLIT preconditioner and set the split using PetscFieldSplitSetIS. This works very well until I try PCREDISTRIBUTE (which is attractive as I have many locked DOFs). I suspect something goes wrong when constructing the IS for the split (I've tried various things using the IS-routines). Can PETSc do this automatically? Or else, any hints?<br>> Kind regards,<br>> Carl-Johan<o:p></o:p></p></div></div></div></div></blockquote></div></div></div></blockquote></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"> <o:p></o:p></div></div></div></div></blockquote></div></div></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div></div></div></div></div></blockquote></div></div></body></html>