<div dir="ltr"><p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">Hello,</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">I’m working on FEM using PETSc.</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">As everyone knows, it is necessary to repeatedly
solve Ax=B.</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">Regarding this, I have 4 questions.</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="gmail-MsoListParagraph" style="margin:0cm 0cm 8pt 38pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">1.<span style="font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"">    
</span></span><span lang="EN-US">There are many steps for preparing
KSPSolve. For example KSPcreate, KSPSetOperators, KSPGetPC, PCSetType, PCFactorSetMatSolverType,
KSPSetFromOptions…<br>
In Nonlinear FEM, there are repeatedly kspsolve for getting answer vector. Is it
correct to do all of the aforementioned processes (KSPcreate, KSPSetOperators ~~~)
for each KSPSolve? Or should I declare it only once at the beginning and not call
it again?</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="gmail-MsoListParagraph" style="margin:0cm 0cm 8pt 38pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">2.<span style="font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"">    
</span></span><span lang="EN-US">If the answer to question 1 is
that it must be repeated every time, should this work be done right before
kspsolve, that is, when the global matrix assembly is finished, or is it
irrelevant to performance at any time?</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="gmail-MsoListParagraph" style="margin:0cm 0cm 8pt 38pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">3.<span style="font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"">    
</span></span><span lang="EN-US">When performing FEM, local
matrices are often scattered in global matrices depending on connectivity. In
this case, which is better in terms of performance: adding the values one by
one with MatSetValue or adding them all at once with MatSetValues even if they
are scattered?</span></p>

<p class="gmail-MsoListParagraph" style="margin:0cm 0cm 8pt 40pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="gmail-MsoListParagraph" style="margin:0cm 0cm 8pt 38pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">4.<span style="font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"">    
</span></span><span lang="EN-US">I would like to measure the time
of each section of the process. Which method is recommended?</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">Thank you for your help.</span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US"> </span></p>

<p class="MsoNormal" style="margin:0cm 0cm 8pt;text-align:justify;line-height:107%;font-size:10pt;font-family:"\00b9d1\00c740  \00ace0\00b515""><span lang="EN-US">Hyung Kim</span></p></div>