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<p class="MsoNormal">Attached are outputs with these options. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What should I make of these? <o:p></o:p></p>
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<p class="MsoNormal"><b>From:</b> Barry Smith <bsmith@petsc.dev> <br>
<b>Sent:</b> Monday, December 6, 2021 2:16 PM<br>
<b>To:</b> Fischer, Greg A. via petsc-users <petsc-users@mcs.anl.gov><br>
<b>Cc:</b> Fischer, Greg A. <fischega@westinghouse.com><br>
<b>Subject:</b> Re: [petsc-users] KSPBuildResidual and KSPType compatibility<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:red">[External Email]</span> <o:p></o:p></p>
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<p class="MsoNormal">What do you get for <span style="font-size:10.5pt;font-family:"Menlo",serif">-ksp_type ibcgs -ksp_monitor -ksp_monitor_true_residual</span>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Menlo",serif">with and without -ksp_pc_side right ?</span>
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<p class="MsoNormal">On Dec 6, 2021, at 12:00 PM, Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">"Fischer, Greg A. via petsc-users" <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> writes:<br>
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<p class="MsoNormal">Hello petsc-users,<br>
<br>
I would like to check convergence against the infinity norm, so I defined my own convergence test routine with KSPSetConvergenceTest. (I understand that it may be computationally expensive.)<br>
<br>
I would like to do this with the "ibcgs" method. When I use KSPBuildResidual and calculate the NORM_2 against the output vector, I get a value that differs from the 2-norm that gets passed into the convergence test function. However, when I switch to the "gcr"
method, the value I calculate matches the function input value.<o:p></o:p></p>
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<p class="MsoNormal"><br>
IBCGS uses the preconditioned norm by default while GCR uses the unpreconditioned norm. You can use -ksp_norm_type unpreconditioned or KSPSetNormType() to make IBCGS use unpreconditioned.<br>
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<p class="MsoNormal">Is the KSPBuildResidual function only compatible with a subset of the KSPType methods? If I want to evaluate convergence against the infinity norm, do I need to set KSPSetInitialGuessNonzero and continually re-start the solver with a lower
tolerance values until I get a satisfactory value of the infinity norm?<br>
<br>
Thanks,<br>
Greg<br>
<br>
<br>
________________________________<br>
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This e-mail may contain proprietary information of the sending organization. Any unauthorized or improper disclosure, copying, distribution, or use of the contents of this e-mail and attached document(s) is prohibited. The information contained in this e-mail
and attached document(s) is intended only for the personal and private use of the recipient(s) named above. If you have received this communication in error, please notify the sender immediately by email and delete the original e-mail and attached document(s).<o:p></o:p></p>
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