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Ling,</div>
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ILU(level) is used for saving storage space with more computations. Normally, we use level=1 or 2. It does not make sense to use level 15. If you have sufficient space, LU would be the best.</div>
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Hong</div>
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<div id="divRplyFwdMsg" dir="ltr"><span style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> petsc-users <petsc-users-bounces@mcs.anl.gov> on behalf of Zou, Ling via petsc-users <petsc-users@mcs.anl.gov><br>
<b>Sent:</b> Wednesday, March 27, 2024 4:24 PM<br>
<b>To:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>Subject:</b> [petsc-users] Does ILU(15) still make sense or should just use LU?</span>
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<p style="margin: 0in; font-family: Aptos, sans-serif; font-size: 12pt;"><span style="font-size: 11pt;">Hi, I’d like to avoid using LU, but in some cases to use ILU and still converge, I have to go to ILU(15), i.e., `-pc_factor_levels 15`. Does it still make
sense, or should I give it up and switch to LU?</span></p>
<p style="margin: 0in; font-family: Aptos, sans-serif; font-size: 12pt;"><span style="font-size: 11pt;"> </span></p>
<p style="margin: 0in; font-family: Aptos, sans-serif; font-size: 12pt;"><span style="font-size: 11pt;">For this particular case, ~2k DoF, and both ILU(15) and LU perform similarly in terms of wall time.</span></p>
<p style="margin: 0in; font-family: Aptos, sans-serif; font-size: 12pt;"><span style="font-size: 11pt;"> </span></p>
<p style="margin: 0in; font-family: Aptos, sans-serif; font-size: 12pt;"><span style="font-size: 11pt;">-Ling</span></p>
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