November 2025 - petsc-users - mailman3.cels.anl.gov

Question about Pseudo Time Stepping
by Aldo Bonfiglioli 20 Apr '26

20 Apr '26

Hi there, I am using -ts_type pseudo to find steady solutions of the Euler/NS PDEs. It looks like FormRHSFunction is called twice with the exactly same value of the dependent variable (u) before invoking TSRHSJacobianFn and then solving the linear system with KSP (u is then updated) > 1 TS dt 0.141197 time 0.141197 > Calling FormRHSFunction; ||u|| = 60.489405479528003 > 463.15635675129079 62.813532026019146 > 5.9789502719351155 > Calling FormRHSFunction; ||u|| = 60.489405479528003 > 463.1563567512907962.8135320260191465.9789502719351155 > Calling TSRHSJacobianFn with ||u|| = 60.489405479528003 > 463.15635675129079 62.813532026019146 > 5.9789502719351155 > Linear solve converged due to CONVERGED_RTOL iterations 9 > Calling FormRHSFunction; ||u|| = > 60.489405476878737463.1563567560218662.8135320316169655.9789502710519811 > 2 TS dt 0.155917 time 0.297115 > Calling FormRHSFunction; ||u|| = > 60.489405476878737463.1563567560218662.8135320316169655.9789502710519811 > Calling FormRHSFunction; ||u|| = > 60.489405476878737463.1563567560218662.8135320316169655.9789502710519811 > Calling TSRHSJacobianFn with ||u|| = > 60.489405476878737463.1563567560218662.8135320316169655.9789502710519811 > Why is it so? Am I possibly misusing (or missing) some options? My .petscrc file is attached. Thank you, Aldo -- Dr. Aldo Bonfiglioli Associate professor of Fluid Mechanics Dipartimento di Ingegneria Universita' della Basilicata V.le dell'Ateneo Lucano, 10 85100 Potenza ITALY tel:+39.0971.205203 fax:+39.0971.205215 web:https://urldefense.us/v3/__http://docenti.unibas.it/site/home/docente.html?m=002423__;!!G_uCfscf7eWS!ci_aySHdF2Qx_B-37IOzELFDtcQRthJ2NItK-JNbfXB0M2_21B_z97WIfjxZUyKCVRRhd1mzL6b-rnCed_i8LLA56JvFdz7JBrw$

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Bug report: petcds fortran module missing?
by Berends, C.J. (Tijn) 27 Nov '25

27 Nov '25

Dear petsc folks, I am trying to set up a very basic example program in Fortran, using Petsc to solve a simple Poisson problem (d2u/dx2 = f). However, I am running into problems when I try to call PetscDSSetResidual to set the function pointers for the residual. According to the documentation, this function is part of the petcds module, but while the header file (petscds.h) exists in my Petsc include directotry, the Fortran module (petscds.mod) does not. Therefore, my code won't compile. I have currently got Petsc installed via Homebrew. I have tried cloning the Petsc git repository and building that, using the configuration option --with-fortran-interfaces=1, but still the petscds.mod file is not there. Am I doing something wrong, or can it be that this particular Fortran interface is just missing? If you need any additional information from me, please let me know. Kind regards, Tijn Berends dr. C. J. (Tijn) Berends Post-doc (palaeo)glaciology Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, The Netherlands Buys Ballot Building (BBG), Room 6.67

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[WARNING: UNSCANNABLE EXTRACTION FAILED]GMRES plus BlockJacobi behave differently for seemlingy identical matrices
by Nils Schween 27 Nov '25

27 Nov '25

Dear PETSc users, Dear PETSc developers, in our software we are solving a linear system with PETSc using GMRES in conjunction with a BlockJacobi preconditioner, i.e. the default of the KSP object. We have two versions of the system matrix, say A and B. The difference between them is the non-zero pattern. The non-zero pattern of matrix B is a subset of the one of matrix A. Their values should be identical. We solve the linear system, using A yields a solution after some iterations, whereas using B does not converge. I created binary files of the two matrices, the right-hand side, and wrote a small PETSc programm, which loads them and demonstrates the issue. I attach the files to this email. We would like to understand why the solver-preconditioner combination works in case A and not in case B. Can you help us finding this out? To test if the two matrices are identical, I substracted them and computed the Frobenius norm of the result. It is zero. To give you more context, we solve a system of partial differential equations that models astrophysical plasmas. It is essentially a system of advection-reaction equations. We use a discontinuous Galerkin (dG) method. Our code relies on the finite element library library deal.ii and its PETSc interface. The system matrices A and B are the result of the (dG) discretisation. We GMRES with a BlockJaboci preconditioner, because we do not know any better. I tested the code I sent with PETSc 3.24.0 and 3.19.1 on my workstation, i.e. Linux home-desktop 6.17.2-arch1-1 #1 SMP PREEMPT_DYNAMIC Sun, 12 Oct 2025 12:45:18 +0000 x86_64 GNU/Linux I use OpenMPI 5.0.8 and I compiled with mpicc, which in my cases use gcc. In case you need more information. Please let me know. Any help is appreciated. Thank you, Nils -- Nils Schween Phone: +49 6221 516 557 Mail: nils.schween(a)mpi-hd.mpg.de PGP-Key: 4DD3DCC0532EE96DB0C1F8B5368DBFA14CB81849 Max Planck Institute for Nuclear Physics Astrophysical Plasma Theory (APT) Saupfercheckweg 1, D-69117 Heidelberg https://www.mpi-hd.mpg.de/mpi/en/research/scientific-divisions-and-groups/i…

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Issue using AOCC + AOCL to build PETSc
by Benjamin Chapman 26 Nov '25

26 Nov '25

Hello, I am currently trying to build PETSc using the AOCC compiler and using AOCL libraries for BLAS/LAPACK. However, I am running into an issue when it tries to download and construct the MPI library, it cannot find the ".libs/libevent.so" library in libevent (which it downloads). I attached the configure.log file. The reason I'm so confused is because PETSc built successfully when I did AOCC + MKL and gcc + AOCL, but not AOCC + AOCL together. Is it even possible to build PETSc using AOCC + AOCL or is it not designed for that? If so, is there a specific procedure I should follow? Thanks in advance. Best, Ben

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41st Colorado Conference on Iterative and Multigrid Methods, June 2026
by Jed Brown 23 Nov '25

23 Nov '25

After many successful Copper Mountain Conferences on Iterative and Multigrid Methods, we have made the difficult decision that it is time to continue the conference series in a new venue. Thus, it is with great pleasure that we announce the 41st Colorado Conference on Iterative and Multigrid Methods, to be held June 21-26, 2026 in Boulder, Colorado, on the CU Campus. We hope to continue the many wonderful traditions of Copper Mountain, with a rich technical problem, opportunities for informal discussion and work time amongst the participants, and a focus on student and early career participants. We are currently finalizing many details for the conference, and information about participation, registration, and lodging will be forthcoming at https://urldefense.us/v3/__https://coloradoconference.github.io/2026/__;!!G… . Expect student paper competition deadlines in February, 2026, and abstract and registration deadlines in Spring, 2026. We look forward to welcoming you in Boulder! Jed Brown, University of Colorado at Boulder Rob Falgout, Lawrence Livermore National Laboratory Scott MacLachlan, Memorial University of Newfoundland Luke Olson, University of Illinois Urbana-Champaign

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Re: [petsc-users] solveBackward in parallel
by Barry Smith 23 Nov '25

23 Nov '25

I would be stunned and amazed if this worked. Sparse factorization codes use very complicated data structures to store the resulting "factors" and the solves are complicated code that traverse through the "factor" data structures to perform the solve. Barry > On Nov 22, 2025, at 6:58 AM, Yin Shi <yin.shi1(a)icloud.com> wrote: > > Thank you very much for your reply. Given this, when using MUMPS in parallel, I can still get the factor matrix (using getFactorMatrix method of a PC object) and use it to do matrix multiplications (e.g., using matMult method of the factor matrix), correct? I also would like to confirm whether the factor matrix returned is really triangular and multiplying it with another matrix gives the intended result. > >> On Nov 16, 2025, at 08:59, Barry Smith <bsmith(a)petsc.dev> wrote: >> >> It appears that only MATSOLVERMKL_CPARDISO provides a parallel backward solve currently. >> >> The only seperation of forward and backward solves in MUMPS appears to be provided with (from its users manual) >> >> A special case is the one >> where the forward elimination step is performed during factorization (see Subsection 3.8), instead of >> during the solve phase. This allows accessing the L factors right after they have been computed, with a >> better locality, and can avoid writing the L factors to disk in an out-of-core context. In this case (forward >> >> >> >>> On Nov 15, 2025, at 9:17 AM, Yin Shi via petsc-users <petsc-users(a)mcs.anl.gov> wrote: >>> >>> Dear Developers, >>> >>> In short, I need to explicitly use A.solveBackward(b, x) in parallel with petsc4py, where A is a Cholesky factored matrix, but it seems that this is not supported (e.g., for mumps and superlu_dist factorization solver backend). Is it possible to work around this? >>> >>> In detail, the problem I need to solve is to generate a set of correlated random numbers (denoted by a vector, w) from an uncorrelated one (denoted by a vector n). Denote the covariance matrix of n as C (symmetric). One needs to first factorize C, C = L L^T, and then solve the linear system L^T w = n for w in parallel. Is it possible to reformulate this problem for it to be implemented using petsc4py? >>> >>> Thank you! >>> Yin >> >

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solveBackward in parallel
by Yin Shi 22 Nov '25

22 Nov '25

Dear Developers, In short, I need to explicitly use A.solveBackward(b, x) in parallel with petsc4py, where A is a Cholesky factored matrix, but it seems that this is not supported (e.g., for mumps and superlu_dist factorization solver backend). Is it possible to work around this? In detail, the problem I need to solve is to generate a set of correlated random numbers (denoted by a vector, w) from an uncorrelated one (denoted by a vector n). Denote the covariance matrix of n as C (symmetric). One needs to first factorize C, C = L L^T, and then solve the linear system L^T w = n for w in parallel. Is it possible to reformulate this problem for it to be implemented using petsc4py? Thank you! Yin

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Ordering of DoFs in submatrices with PCFieldsplit
by Blauth, Sebastian 19 Nov '25

19 Nov '25

Dear PETSc developers and users, I have a question regarding the Fieldsplit preconditioner in PETSc. In particular, I want to know how the submatrices there are created from the parent matrix. The "obvious" way would be to take the DoF indices of the corresponding split and "renumber" them so that the DoFs in the submatrix have the same order as the ones of the parent matrix. I did not find any documentation on this and as it is at least possible that the DoFs are re-ordered, I wanted to ask this question. Obviously, in case the DoFs are re-ordered, how can I get the mapping between the DoFs of the parent and the submatrix? The thing I am wanting to work on is implementing a pressure convection diffusion preconditioner with FEniCS for the incompressible Navier-Stokes equations. The parent matrix is assembled via a mixed FEM and then I use PETSc to solve the system. I want to assemble the corresponding operators on the pressure space from a collapsed (i.e. sub-space of the mixed FEM) function space. However, FEniCS re-orders the DoFs there, but I can get a mapping between the DoFs so this should not be problematic. However, I am not sure if PETSc also does a re-ordering. Thanks a lot in advance and best regards, Sebastian -- Dr. Sebastian Blauth Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM Abteilung Transportvorgänge Fraunhofer-Platz 1, 67663 Kaiserslautern Telefon: +49 631 31600-4968 sebastian.blauth(a)itwm.fraunhofer.de<mailto:[email protected]> https://urldefense.us/v3/__https://www.itwm.fraunhofer.de__;!!G_uCfscf7eWS!… <https://urldefense.us/v3/__https://www.itwm.fraunhofer.de/__;!!G_uCfscf7eWS… >

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Petsc + nvhpc
by howen 17 Nov '25

17 Nov '25

Dear All, I am interfacing our CFD code (Fortran + OpenACC) to Petsc. Since we use OpenACC the natural choice for us is to use Nvidia´s nvhpc compiler. The Gnu compiler does not work well and we do not have access to the Cray compiler. I already know that the latest version of Petsc does not compile with nvhpc, I am therefore using version 3.21. I get good results on the CPU both in serial and parallel (MPI). However, the GPU implementation, that is what we are interested in, only work correctly for the serial version. In parallel, the results are different. Even for a CG solve. I would like to know, if you have experience with the Nvidia compiler. I am particularly interested if you have already observed issues with it. Your opinion on whether to put further effort into trying to find a bug I may have introduced during the interfacing is highly appreciated. Best, Herbert Owen Senior Researcher, Dpt. Computer Applications in Science and Engineering Barcelona Supercomputing Center (BSC-CNS) Tel: +34 93 413 4038 Skype: herbert.owen https://urldefense.us/v3/__https://scholar.google.es/citations?user=qe5O2IY…

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Probelm with DMPlexExtractSubMesh
by Aldo Bonfiglioli 17 Nov '25

17 Nov '25

Dear all, I am having troubles in using DMPlexExtractSubMesh to extract the different strata of the Face Sets of a given mesh. When run on the enclosed tetrahedral mesh of the unit cube generated with gmsh > Face Sets: 6 strata with value/size (1 (246), 2 (246), 3 (246), 4 > (246), 5 (242), 6 (242)) > I would expect 246 "points" on stratum 3, but when I DMview the subdm (and plot it) the surface mesh looks incomplete > DM Object: patch_03 1 MPI process > type: plex > patch_03 in 2 dimensions: > Cells are at height 1 > Number of 0-cells per rank: 122 > Number of 1-cells per rank: 325 > Number of 2-cells per rank: 204 > Number of 3-cells per rank: 204 [204] > Labels: > celltype: 4 strata with value/size (0 (122), 1 (325), 3 (204), 12 (204)) > depth: 4 strata with value/size (0 (122), 1 (325), 2 (204), 3 (204)) > Cell Sets: 1 strata with value/size (1 (204)) > Face Sets: 1 strata with value/size (3 (204)) > Edge Sets: 2 strata with value/size (1 (8), 5 (8)) > see also patch_03.pdf What am I doing wrong? A simple reproducer (compiles with petsc-3.24.0) and the gmsh mesh are enclosed. Thanks, Aldo -- Dr. Aldo Bonfiglioli Associate professor of Fluid Mechanics Dipartimento di Ingegneria Universita' della Basilicata V.le dell'Ateneo Lucano, 10 85100 Potenza ITALY tel:+39.0971.205203 fax:+39.0971.205215 web:https://urldefense.us/v3/__http://docenti.unibas.it/site/home/docente.html?m=002423__;!!G_uCfscf7eWS!aMKmGG4aim9XcbNSnDyHUkDyhUkQHGZ-u-xX2C-sycYUMmtTij6AwqsQbZPXJSvPp9KUfgwRJK2Ok6Me2BLgO0en1w4QF2fHo7s$

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