<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div> BoomerAMG will never simply solve the resulting linear system. Mixing elliptic and hyperbolic equations into a linear system and then trying a "black-box" solver will never work.<div class=""><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Apr 11, 2021, at 11:35 PM, sthavishtha bhopalam <<a href="mailto:sthavishthabr@gmail.com" class="">sthavishthabr@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small">I am solving the isothermal form of the Navier-Korteweg system of equations - it's mixed hyperbolic-elliptic in nature.</div><div class=""><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><font size="2" face="verdana, sans-serif" class="">-------------------------------------------</font></div><div class=""><font size="2" face="verdana, sans-serif" class="">Regards</font></div><div dir="ltr" class=""><font face="verdana, sans-serif" class=""><br class=""></font><div class=""><font face="verdana, sans-serif" class="">Sthavishtha Bhopalam Rajakumar</font></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div></div></div></div></div></div></div><br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Apr 11, 2021 at 11:37 PM Matthew Knepley <<a href="mailto:knepley@gmail.com" class="">knepley@gmail.com</a>> wrote:<br class=""></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" class=""><div dir="ltr" class="">On Sun, Apr 11, 2021 at 1:37 PM sthavishtha bhopalam <<a href="mailto:sthavishthabr@gmail.com" target="_blank" class="">sthavishthabr@gmail.com</a>> wrote:<br class=""></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"><div dir="ltr" class=""><div style="font-family:verdana,sans-serif;font-size:small" class="">Hello PETSc users</div><div style="font-family:verdana,sans-serif;font-size:small" class=""><br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class="">I am trying to experiment with Hypre's BoomerAMG preconditioner which continually yields the error message "Linear solve did not converge due to DIVERGED_DTOL iterations 1". I would appreciate if someone can suggest some ways I could get BoomerAMG to yield converged results - the attached output shows a snippet of the error message. <u class="">Command Line options I used for BoomerAMG</u> : <i class=""><span style="font-family:"comic sans ms",sans-serif" class="">-pc_type hypre -pc_hypre_type boomeramg -pchypreboomeramgtol 1.0e-3 -pchypreboomeramgstrongthreshold 0.25 -ksp_type richardson -pc_hypre_boomeramg_max_iter 6 -snes_rtol 1.0e-3 -ksp_rtol 1.0e-3 -ksp_view -snes_view -ksp_monitor -snes_monitor -ksp_max_it 100 -ksp_converged_reason -snes_converged_reason</span></i></div><div style="font-family:verdana,sans-serif;font-size:small" class=""><br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class="">I also tried using <span style="font-family:"comic sans ms",sans-serif" class=""><i class="">-ksp_type gmres</i></span>, different values of <i class=""><span style="font-family:"comic sans ms",sans-serif" class="">-pc_hypre_boomeramg_max_iter</span></i>, <span style="font-family:"comic sans ms",sans-serif" class=""><i class="">-pchypreboomeramgstrongthreshold</i></span>, <i class=""><span style="font-family:"comic sans ms",sans-serif" class="">-ksp_initial_guess_nonzero</span></i> but all yielded the same error message.<br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class=""><br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class="">However, the direct solver converges as required - the attached output shows a snippet of the norms from the SNES and KSP.<br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class=""><u class="">Command Line options I used for the direct solver</u> : <i class=""><span style="font-family:"comic sans ms",sans-serif" class="">-ksp_type gmres -pc_type lu -pc_factor_shift_type nonzero -pc_factor_mat_solver_type mumps -snes_converged_reason -ksp_converged_reason -ksp_rtol 1e-3 -snes_rtol 1e-3 -ksp_monitor -snes_monitor</span></i></div><div style="font-family:verdana,sans-serif;font-size:small" class=""><br class=""></div><div style="font-family:verdana,sans-serif;font-size:small" class="">There is no particular reason for using the AMG here, but I just wanted to familiarize with it's options to see which of them need to be particularly tuned to yield converged and correct results.</div></div></blockquote><div class=""><br class=""></div><div class="">Hypre is only going to work for a very specific set of systems. What are you solving?</div><div class=""><br class=""></div><div class=""> Thanks,</div><div class=""><br class=""></div><div class=""> Matt</div><div class=""> </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" class=""><div style="font-family:verdana,sans-serif;font-size:small" class="">Thanks<br clear="all" class=""></div><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><font size="2" face="verdana, sans-serif" class="">-------------------------------------------</font></div><div class=""><font size="2" face="verdana, sans-serif" class="">Regards</font></div><div dir="ltr" class=""><font face="verdana, sans-serif" class=""><br class=""></font><div class=""><font face="verdana, sans-serif" class="">Sthavishtha <br class=""></font></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div></div></div></div></div></div></div></div>
</blockquote></div><br clear="all" class=""><div class=""><br class=""></div>-- <br class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class=""><div dir="ltr" class=""><div class="">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br class="">-- Norbert Wiener</div><div class=""><br class=""></div><div class=""><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank" class="">https://www.cse.buffalo.edu/~knepley/</a><br class=""></div></div></div></div></div></div></div></div>
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