Il 07/11/25 02:10, Barry Smith ha scritto:
On Nov 6, 2025, at 4:11 AM, Stefano Zampini <[email protected]> wrote:Matteoeventually (and in some sense counterintuitively) the DM stores the information on the problem, not SNES."The information on the problem" here means the function you set with SNESSetFunction, SNESSetJacobian etc. (and possibly other stuff, I am not sure).
Oddly, sometimes the two SNES seems to work nevertheless, but after your anwers I will make sure that I explicitly DMClone when I need more that 1 snes.
Matteo
See the snippet below to make things more clear SNESSetDM(snes1,dm) SNESSetFunction(snes1,F) SNESSolve(snes1) // Solves F(x)=0 SNESSetDM(snes2,dm) SNESSetFunction(snes2,G) SNESSolve(snes2) // Solves G(x)=0 SNESSolve(snes1) // Solves G(x), not F(x)!!If you have a plex you can call DMClone(dm,dm2) and set a new section on dm2 to be used on snes2 (the mesh won't be duplicated, only the problem dependent part) I guess you can follow the same approach with a DMDA, it should work. If not, you may need to call DMDuplicate on the DMDA.Il giorno gio 6 nov 2025 alle ore 11:19 Matteo Semplice via petsc-users <[email protected]> ha scritto:Dear Barry, sorry for jumping into this. I am wondering if your reply is related to DMDA or to DM in general. I have at least one code where I do something similar to what Samuele did in his sample code: create a DMPlex, create a section on this DMPlex, create two SNES solving for Vecs defined on that same section and attach to each of them a different SNESFunction and SNESJacobian (one solves a predictor and the other is a corrector). Everything seems fine, but I am wondering if that code is somewhat weak and should be changed by DMCloning the plex as you suggested to Samuele. Thanks Matteo On 06/11/2025 07:49, Samuele Ferri wrote:-- Prof. Matteo Semplice[email protected] sembra simile a un utente che in precedenza ti ha inviato un messaggio di posta elettronica, ma potrebbe non essere lo stesso. Scopri perché potrebbe trattarsi di un rischio <https://urldefense.us/v3/__https://aka.ms/LearnAboutSenderIdentification__;!!G_uCfscf7eWS!d2x1h3Pt9OqhfeBcqW8pR0dbGy3bRw6bM-p0DxGAaY0CXWkqH3lpsuXiob9mOqfsy-aRVJXUig3819n2CWpYyFn4FDaTAWRxNDXZsA$> Dear Barry, thank you for your reply. Now everything works fine. Best regards Samuele ------------------------------------------------------------------------ *Da:* Barry Smith <[email protected]> <mailto:[email protected]> *Inviato:* mercoledì 5 novembre 2025 15:47 *A:* Samuele Ferri <[email protected]> <mailto:[email protected]> *Cc:* [email protected] <[email protected]> <mailto:[email protected]> *Oggetto:* Re: [petsc-users] Two SNES on the same DM not working This is not supported. Duplicate your DM.On Nov 5, 2025, at 9:17 AM, Samuele Ferri <[email protected]> <mailto:[email protected]> wrote: Dear petsc users, in petsc version 3.24, I'm trying to create two snes over the same DM, but with different functions and jacobians. Despite making different calls to SNESSetFunction it happens the second snes uses the same function of the first. Can you help me finding the problem, please? Here below there is a minimal working example showing the issue: static char help[] = "Test SNES.\n"; #include <petscsys.h> #include <petscdmda.h> #include <petscsnes.h> PetscErrorCode Jac_1(SNES/snes/, Vec/x/, Mat/J/, Mat/B/, void *){ PetscFunctionBegin; printf("Jac 1\n"); PetscFunctionReturn(PETSC_SUCCESS); } PetscErrorCode Function_1(SNES/snes/, Vec/x/, Vec/f/, void *){ PetscFunctionBegin; printf("Function 1\n"); PetscFunctionReturn(PETSC_SUCCESS); } PetscErrorCode Jac_2(SNES/snes/, Vec/x/, Mat/J/, Mat/B/, void *){ PetscFunctionBegin; printf("Jac 2\n"); PetscFunctionReturn(PETSC_SUCCESS); } PetscErrorCode Function_2(SNES/snes/, Vec/x/, Vec/f/, void *){ PetscFunctionBegin; printf("Function 2\n"); PetscFunctionReturn(PETSC_SUCCESS); } int main(int/argc/, char **/argv/) { PetscFunctionBeginUser; PetscCall(PetscInitialize(&/argc/, &/argv/, NULL, help)); DM dm; PetscCall(DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, 100, 1, 1, NULL, &dm)); PetscCall(DMSetFromOptions(dm)); PetscCall(DMSetUp(dm)); SNES snes1, snes2; Vec r1,r2; Mat J1, J2; PetscCall(DMCreateGlobalVector(dm, &r1)); PetscCall(DMCreateGlobalVector(dm, &r2)) PetscCall(DMCreateMatrix(dm, &J1)); PetscCall(DMCreateMatrix(dm, &J2)); PetscCall(SNESCreate(PETSC_COMM_WORLD, &snes1)); PetscCall(SNESCreate(PETSC_COMM_WORLD, &snes2)); PetscCall(SNESSetType(snes1, SNESNEWTONLS)); PetscCall(SNESSetType(snes2, SNESNEWTONLS)); PetscCall(SNESSetFromOptions(snes1)); PetscCall(SNESSetFromOptions(snes2)); PetscCall(SNESSetFunction(snes1, r1, Function_1, NULL)); PetscCall(SNESSetFunction(snes2, r2, Function_2, NULL)); PetscCall(SNESSetJacobian(snes1, J1, J1, Jac_1, NULL)); PetscCall(SNESSetJacobian(snes2, J2, J2, Jac_2, NULL)); PetscCall(SNESSetDM(snes1, dm)); PetscCall(SNESSetDM(snes2, dm)); PetscCall(SNESSolve(snes1, NULL, NULL)); PetscCall(SNESSolve(snes2, NULL, NULL)); printf("snes1 %p; snes2 %p\n", snes1, snes2); SNESFunctionFn *p; PetscCall(SNESGetFunction(snes1, NULL, &p, NULL)); printf("snes1: pointer %p, true function %p\n", *p, Function_1); PetscCall(SNESGetFunction(snes2, NULL, &p, NULL)); printf("snes2: pointer %p, true function %p\n", *p, Function_2); PetscCall(PetscFinalize()); PetscFunctionReturn(PETSC_SUCCESS); }Università degli Studi dell’Insubria Dipartimento di Scienza e Alta Tecnologia – DiSAT Professore Associato Via Valleggio, 11 – 22100 Como (CO) – Italia tel.: +39 031 2386316 -- Stefano
-- --- Professore Associato in Analisi Numerica Dipartimento di Scienza e Alta Tecnologia Università degli Studi dell'Insubria Via Valleggio, 11 - Como
