<div dir="ltr"><div dir="ltr">On Tue, Sep 28, 2021 at 8:39 AM TARDIEU Nicolas via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>Dear PETSc Team,<br>
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<div>We, code_aster's development team, are using PETSc in our application for years now, mainly for the KSP et PC features. We run tests cases every week without problems.<br>
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After upgrading from PETSc 3.12.3 to <span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:16px;background-color:rgb(255,255,255)">3.15.3, a test case using GMRES failed with KSP_DIVERGED_BREAKDOWN. By rolling back to 3.12.3, we have
checked that the upgrade is the origin of the failure.</span>
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<div>We know this can occur with GMRES but it is the first time we are facing this situation. <br>
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<p>Is it a bug ? If yes, how can we help to fix it ? If no, what can we do ? Could the flexible version of GMRES be an alternative ?</p></div></div></blockquote><div>This is not a bug, but we did change the operation. We now check whether there is a significant residual spike after a restart. We</div><div>want to let the user know that this likely means that the solver is inappropriate for the problem. As Jose notes, you can turn off this</div><div>behavior.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr" style="font-size:12pt;color:rgb(0,0,0);background-color:rgb(255,255,255);font-family:Calibri,Arial,Helvetica,sans-serif"><div>
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<div style="margin:0px"><font size="3" face="Calibri,sans-serif">Best regards, </font>
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<div style="margin:0px"><font face="Calibri,sans-serif"><font size="3">Nicolas<br>
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</font><font size="2" face="Arial,sans-serif" color="#ff8100"><span style="font-size:9pt"><b>Nicolas Tardieu</b></span></font><br>
<div style="margin:0px"><font size="2" face="Calibri,sans-serif"><span style="font-size:11pt"><font size="1" face="Arial,sans-serif" color="#ff8100"><span style="font-size:8pt"><b>Ing, PhD</b></span></font></span></font></div>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><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.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>