Great, thanks for the input so far. We will wait for Matt's response soonish.
Sincerely, Joe Alexandersen Associate Professor DFF Sapere Aude Research Leader The Faculty of Engineering Institute of Mechanical and Electrical Engineering SDU Mechanical Engineering T +45 65 50 74 65 M +45 93 50 72 44 j...@sdu.dk https://urldefense.us/v3/__http://www.sdu.dk/ansat/joal__;!!G_uCfscf7eWS!aMq_eBTTAvLdy-GtpWdAVq8zqDaObi_eL0EKi7yFbh6VUSQCx-pDonMSd9Rejkpr3DBMyE15NaaOKv14zQ$ University of Southern Denmark Campusvej 55 DK-5230 Odense M https://urldefense.us/v3/__http://www.sdu.dk__;!!G_uCfscf7eWS!aMq_eBTTAvLdy-GtpWdAVq8zqDaObi_eL0EKi7yFbh6VUSQCx-pDonMSd9Rejkpr3DBMyE15NaYjcKBeNw$ Sent from Outlook for Android<https://urldefense.us/v3/__https://aka.ms/AAb9ysg__;!!G_uCfscf7eWS!aMq_eBTTAvLdy-GtpWdAVq8zqDaObi_eL0EKi7yFbh6VUSQCx-pDonMSd9Rejkpr3DBMyE15NaYUzarulQ$ > ________________________________ From: Mark Adams <mfad...@lbl.gov> Sent: Thursday, March 20, 2025 5:00:31 pm To: Barry Smith <bsm...@petsc.dev> Cc: Joe Alexandersen <j...@sdu.dk>; petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov> Subject: Re: [petsc-users] Semi-coarsening for GMG using DMDA? You don't often get email from mfad...@lbl.gov. Learn why this is important<https://urldefense.us/v3/__https://aka.ms/LearnAboutSenderIdentification__;!!G_uCfscf7eWS!aMq_eBTTAvLdy-GtpWdAVq8zqDaObi_eL0EKi7yFbh6VUSQCx-pDonMSd9Rejkpr3DBMyE15NaasFl50jQ$ > We have worked on semi coarsening in DMPlex, but it is not finished and we are not working on it now. I'm not sure about how easy it would be in DMDA, but Barry is suggesting that it is doable. We need to wait for Matt and he is on travel so his response may be delayed. Mark On Thu, Mar 20, 2025 at 11:34 AM Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>> wrote: In theory you can do as you propose. In the context below uniform refinement" only means that the coordinates of the DMDA are ignored so each refinement. The interpolation is fine woth different refinements in the different coordinate directions. Barry On Mar 20, 2025, at 5:56 AM, Joe Alexandersen via petsc-users <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> wrote: Dear PETSc developers, We are working with a code that uses regular meshes (DMDA) and geometric multigrid. We would like to go from uniform coarsening/refinement to semi-coarsening/refinement, due to anisotropy in our underlying equations. We have tried to figure out if we can do this using built-in functions of PETSc, but it is unclear to us whether we can get it done relatively easily. It seems that we can go from the coarsest grid and refine differently in each direction using DMDASetRefinementFactor and then use DMRefine to define the finer levels. However, from the doc page for DMCreateInterpolation, it states that it only works for "uniform refinement" which to me seems to indicate it will not work with different refinement in each direction. But on the other hand, it states that it should work if using DMRefine, which I assume used the information from DMDASetRefinementFactor upon creation? So our questions are: is there are feasible and relatively simple way to do semi-coarsening/refinement of DMDAs for geometric multigrid hierarchies? Would the above work? Thanks in advance! Sincerely, Joe Alexandersen University of Southern Denmark
