<div dir="ltr">I want to use METIS for ordering. <br>I heard the MUMPS has good performance with METIS ordering.<div><br></div><div>However there are some wonder things.</div><div>1. With option "-mpi_linear_solver_server -ksp_type preonly -pc_type mpi -mpi_pc_type lu " the MUMPS solving is slower than with option "-mpi_linear_solver_server -pc_type mpi -ksp_type preonly". <br> Why does this result happen?</div><div><br></div><div><br></div><div>2. (MPIRUN case (actually, mpi_linear_solver_server case))) In my code, there is already has "PetscCall(PCSetType(pc,PCLU))" . However, to use METIS by using "-mpi_mat_mumps_icntl_7 5" I must append this option "-mpi_pc_type pu".<br>If I don't apply "-mpi_pc_type lu", the metis option ("-mpi_mat_mumps_icntl_7 5"). Can I get some information about this? </div><div><br><div><br></div><div><br></div><div>Thanks, </div><div>Hyung Kim</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">2022년 12월 7일 (수) 오전 12:24, Barry Smith <<a href="mailto:bsmith@petsc.dev" target="_blank">bsmith@petsc.dev</a>>님이 작성:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><br><div><br><blockquote type="cite"><div>On Dec 6, 2022, at 5:15 AM, 김성익 <<a href="mailto:ksi2443@gmail.com" target="_blank">ksi2443@gmail.com</a>> wrote:</div><br><div><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><div 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><br></div><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 have some questions about pc and mumps_icntl.</span></p><p 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">What’s the difference between adopt
preconditioner by code (for example, PetscCall(PCSetType(pc,PCLU)) and option -pc_type
lu??<br>
And also, What’s the priority between code pcsettype and option -pc_type ??<br>
<br>
</span></p><p 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">When I tried to use METIS in MUMPS,
I adopted metis by option (for example, -mat_mumps_icntl_7 5). In this situation,
it is impossible to use metis without pc_type lu. However, in my case pc type lu
makes the performance poor. So I don’t want to use lu preconditioner. How can I
do this?</span></p></div></div></blockquote><div> The package MUMPS has an option to use metis in its ordering process which can be turned on as indicated while using MUMPS. Most preconditioners that PETSc can use do not use metis for any purpose hence there is no option to turn on its use. For what purpose do you wish to use metis? Partitioning, ordering, ?</div><div><br></div><div><br></div> <br><blockquote type="cite"><div><div dir="ltr"><div 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><br></div><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">Thanks,</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>
</div></blockquote></div><br></div></blockquote></div></div>