<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> SuperLU_DIST won't "magically" run on saddle point problems. It only does limited pivoting, realistically a parallel LU cannot always do complete pivoting or it becomes a sequential algorithm. For parallel you need to use PCFIELDSPLIT, for sequential you can use SuperLU (not SuperLU_DIST) since it can do more pivoting, being a sequential algorithm.<div class=""><br class=""></div><div class=""> Barry</div><div class=""><br class=""><div class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Jul 28, 2020, at 7:59 PM, Bin Liu <<a href="mailto:lbllm2018@hotmail.com" class="">lbllm2018@hotmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 18px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">Thanks for your tutorials. Yes. I tried PCFIELDSPLIT. However, it only works for sequential runs. When I run the code in distributed memory, it reports errors. In fact, the essence of my wonder is (a) how to set up superlu_dist in petsc for solving saddle point problem in distributed memory? (b) does the direct solvers in petsc can run in distributed memory for solving saddle point problem?<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><a name="_MailEndCompose" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></a></div><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(225, 225, 225); padding: 3pt 0cm 0cm;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><b class=""><span lang="EN-US" style="font-size: 11pt; font-family: Calibri, sans-serif;" class="">From:</span></b><span lang="EN-US" style="font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="Apple-converted-space"> </span>Stefano Zampini [<a href="mailto:stefano.zampini@gmail.com" style="color: purple; text-decoration: underline;" class="">mailto:stefano.zampini@gmail.com</a>]<span class="Apple-converted-space"> </span><br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Tuesday, 28 July 2020 6:55 PM<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Bin Liu <<a href="mailto:lbllm2018@hotmail.com" style="color: purple; text-decoration: underline;" class="">lbllm2018@hotmail.com</a>><br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:petsc-users@mcs.anl.gov" style="color: purple; text-decoration: underline;" class="">petsc-users@mcs.anl.gov</a><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [petsc-users] solving saddle point problem in distributed memory<o:p class=""></o:p></span></div></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class="">If you want advice you should post the error trace PETSc reports.<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class="">Anyway, solving Stokes is not so trivial (without direct solvers, you may need mesh dependent information), but we have examples for it<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><a href="https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex42.c" style="color: purple; text-decoration: underline;" class="">https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex42.c</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><a href="https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex43.c" style="color: purple; text-decoration: underline;" class="">https://gitlab.com/petsc/petsc/-/blob/master/src/ksp/ksp/tutorials/ex43.c</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><a href="https://gitlab.com/petsc/petsc/-/blob/master/src/snes/tutorials/ex69.c" style="color: purple; text-decoration: underline;" class="">https://gitlab.com/petsc/petsc/-/blob/master/src/snes/tutorials/ex69.c</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class="">If you scroll to the end of those files, you see a bunch of possible options either using PCFIELDSPLIT, PCBDDC or KSPFETIDP.<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><br class=""><br class=""><o:p class=""></o:p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class="">On Jul 28, 2020, at 12:37 PM, Bin Liu <<a href="mailto:lbllm2018@hotmail.com" style="color: purple; text-decoration: underline;" class="">lbllm2018@hotmail.com</a>> wrote:<o:p class=""></o:p></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div><div class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class="">I would like to solve a saddle point problem arising from the stokes equation. I got successful to use the direct solvers in sequential runs. However, I would like to extend it for distributed memory computation. I tried to use superlu_dist, but the program returns errors. Is it possible to solve a saddle point problem in distributed memory using superlu_dist? Could anyone give a simple sample code to set up the parameters of the solver?<o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class="">Thanks</span></div></div></div></blockquote></div></div></div></div></blockquote></div><br class=""></div></div></body></html>