In any case, we need to activate PetscCheck in debug mode too. This could have been avoided.
Il giorno gio 13 lug 2023 alle ore 18:23 Karin&NiKo <niko.ka...@gmail.com> ha scritto: > Thank you very much for the information Matt. > Unfortunately, I do not use DM.... :-( > > Le jeu. 13 juil. 2023 à 13:44, Matthew Knepley <knep...@gmail.com> a > écrit : > >> On Thu, Jul 13, 2023 at 5:33 AM Pierre Jolivet <pierre.joli...@lip6.fr> >> wrote: >> >>> Dear Nicolas, >>> >>> On 13 Jul 2023, at 10:17 AM, TARDIEU Nicolas <nicolas.tard...@edf.fr> >>> wrote: >>> >>> Dear Pierre, >>> >>> You are absolutely right. I was using a --with-debugging=0 (aka release) >>> install and this is definitely an error. >>> Once I used my debug install, I found the way to fix my problem. The >>> solution is in the attached script: I first need to extract the correct >>> block from the PC operator's MatNest and then append the null space to it. >>> Anyway this is a bit tricky... >>> >>> >>> Yep, it’s the same with all “nested” solvers, fieldsplit, ASM, MG, you >>> name it. >>> You first need the initial PCSetUp() so that the bare minimum is put in >>> place, then you have to fetch things yourself and adapt it to your needs. >>> We had a similar discussion with the MEF++ people last week, there is >>> currently no way around this, AFAIK. >>> >> >> Actually, I hated this as well, so I built a way around it _if_ you are >> using a DM to define the problem. Then >> you can set a "nullspace constructor" to make it if the field you are >> talking about is ever extracted. You use DMSetNullSpaceConstructor(). I do >> this in SNES ex62 and ex69, and other examples. >> >> Thanks, >> >> Matt >> >> >>> Thanks, >>> Pierre >>> >>> Regards, >>> Nicolas >>> >>> ------------------------------ >>> *De :* pierre.joli...@lip6.fr <pierre.joli...@lip6.fr> >>> *Envoyé :* mercredi 12 juillet 2023 19:52 >>> *À :* TARDIEU Nicolas <nicolas.tard...@edf.fr> >>> *Cc :* petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov> >>> *Objet :* Re: [petsc-users] Near null space for a fieldsplit in petsc4py >>> >>> >>> > On 12 Jul 2023, at 6:04 PM, TARDIEU Nicolas via petsc-users < >>> petsc-users@mcs.anl.gov> wrote: >>> > >>> > Dear PETSc team, >>> > >>> > In the attached example, I set up a block pc for a saddle-point >>> problem in petsc4py. The IS define the unknowns, namely some physical >>> quantity (phys) and a Lagrange multiplier (lags). >>> > I would like to attach a near null space to the physical block, in >>> order to get the best performance from an AMG pc. >>> > I have been trying hard, attaching it to the initial block, to the IS >>> but no matter what I am doing, when it comes to "ksp_view", no near null >>> space is attached to the matrix. >>> > >>> > Could you please help me figure out what I am doing wrong ? >>> >>> Are you using a double-precision 32-bit integers real build of PETSc? >>> Is it --with-debugging=0? >>> Because with my debug build, I get the following error (thus explaining >>> why it’s not attached to the KSP). >>> Traceback (most recent call last): >>> File "/Volumes/Data/Downloads/test/test_NullSpace.py", line 35, in >>> <module> >>> ns = NullSpace().create(True, [v], comm=comm) >>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >>> File "petsc4py/PETSc/Mat.pyx", line 5611, in >>> petsc4py.PETSc.NullSpace.create >>> petsc4py.PETSc.Error: error code 62 >>> [0] MatNullSpaceCreate() at >>> /Volumes/Data/repositories/petsc/src/mat/interface/matnull.c:249 >>> [0] Invalid argument >>> [0] Vector 0 must have 2-norm of 1.0, it is 22.3159 >>> >>> Furthermore, if you set yourself the constant vector in the near >>> null-space, then the first argument of create() must be False, otherwise, >>> you’ll have twice the same vector, and you’ll end up with another error >>> (the vectors in the near null-space must be orthonormal). >>> If things still don’t work after those couple of fixes, please feel free >>> to send an up-to-date reproducer. >>> >>> Thanks, >>> Pierre >>> >>> > Thanks, >>> > Nicolas >>> > >>> > >>> > >>> > >>> > Ce message et toutes les pièces jointes (ci-après le 'Message') sont >>> établis à l'intention exclusive des destinataires et les informations qui y >>> figurent sont strictement confidentielles. 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The information contained in this Message is >>> confidential. Any use of information contained in this Message not in >>> accord with its purpose, any dissemination or disclosure, either whole or >>> partial, is prohibited except formal approval. >>> > >>> > If you are not the addressee, you may not copy, forward, disclose or >>> use any part of it. If you have received this message in error, please >>> delete it and all copies from your system and notify the sender immediately >>> by return message. >>> > >>> > E-mail communication cannot be guaranteed to be timely secure, error >>> or virus-free. >>> > <test.tgz> >>> >>> >>> Ce message et toutes les pièces jointes (ci-après le 'Message') sont >>> établis à l'intention exclusive des destinataires et les informations qui y >>> figurent sont strictement confidentielles. Toute utilisation de ce Message >>> non conforme à sa destination, toute diffusion ou toute publication totale >>> ou partielle, est interdite sauf autorisation expresse. >>> Si vous n'êtes pas le destinataire de ce Message, il vous est interdit >>> de le copier, de le faire suivre, de le divulguer ou d'en utiliser tout ou >>> partie. Si vous avez reçu ce Message par erreur, merci de le supprimer de >>> votre système, ainsi que toutes ses copies, et de n'en garder aucune trace >>> sur quelque support que ce soit. Nous vous remercions également d'en >>> avertir immédiatement l'expéditeur par retour du message. >>> Il est impossible de garantir que les communications par messagerie >>> électronique arrivent en temps utile, sont sécurisées ou dénuées de toute >>> erreur ou virus. >>> ____________________________________________________ >>> This message and any attachments (the 'Message') are intended solely for >>> the addressees. The information contained in this Message is confidential. >>> Any use of information contained in this Message not in accord with its >>> purpose, any dissemination or disclosure, either whole or partial, is >>> prohibited except formal approval. >>> If you are not the addressee, you may not copy, forward, disclose or use >>> any part of it. If you have received this message in error, please delete >>> it and all copies from your system and notify the sender immediately by >>> return message. >>> E-mail communication cannot be guaranteed to be timely secure, error or >>> virus-free. >>> <test_NullSpace.py.gz> >>> >>> >>> >> >> -- >> What most experimenters take for granted before they begin their >> experiments is infinitely more interesting than any results to which their >> experiments lead. >> -- Norbert Wiener >> >> https://www.cse.buffalo.edu/~knepley/ >> <http://www.cse.buffalo.edu/~knepley/> >> > -- Stefano
