# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=31 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 32 --- ## [Résolution de deux système](https://community.freefem.org/t/resolution-de-deux-systeme/2535)
**Author:** [@aweni](https://community.freefem.org/u/aweni)\ **Replies:** 6\ **Last updated:** [June 12, 2023, 8:48pm UTC](https://community.freefem.org/t/resolution-de-deux-systeme/2535 "2023-06-12T20:48:39Z")
Bonsoir à tous comment écrire un code où je veux récupérer la solution du premier système pour résoudre le second système. C’est à dire je veux récupérer la solution pour la résolution du système 2 --- ## [Legend of vec value iso value in plotting](https://community.freefem.org/t/legend-of-vec-value-iso-value-in-plotting/2539)
**Author:** [@gnaganlu](https://community.freefem.org/u/gnaganlu)\ **Replies:** 0\ **Last updated:** [June 12, 2023, 9:15am UTC](https://community.freefem.org/t/legend-of-vec-value-iso-value-in-plotting/2539 "2023-06-12T09:15:02Z")
Hello, In plotting, the legend of vec value and iso value has too many decimals and all numbers are too close to each other. Is there any way to write these numbers far from each other and with fewer decimal points in t… --- ## [Problems defining a non-linear form](https://community.freefem.org/t/problems-defining-a-non-linear-form/2537)
**Author:** [@jtermens](https://community.freefem.org/u/jtermens)\ **Replies:** 2\ **Last updated:** [June 12, 2023, 8:30am UTC](https://community.freefem.org/t/problems-defining-a-non-linear-form/2537 "2023-06-12T08:30:32Z")
Hello everyone, I have a running code that solves two linear equations successively: first I solve for a polarity vector and then I solve for the velocity vector in a force balance equation with some forces depending on… --- ## [A higher BDM element in Freefem](https://community.freefem.org/t/a-higher-bdm-element-in-freefem/2531)
**Author:** [@junjie](https://community.freefem.org/u/junjie)\ **Replies:** 4\ **Last updated:** [June 10, 2023, 11:03am UTC](https://community.freefem.org/t/a-higher-bdm-element-in-freefem/2531 "2023-06-10T11:03:53Z")
Hello everyone. I’m trying to solve the Stokes equations with BDM element in Freefem. However, there seems to be only BDM1 element. It’s so frustrating. Because I want to verify the convergence-order of the error with a… --- ## [Symmetric boundary condition not satisfied](https://community.freefem.org/t/symmetric-boundary-condition-not-satisfied/2527)
**Author:** [@KanLi](https://community.freefem.org/u/KanLi)\ **Replies:** 5\ **Last updated:** [June 10, 2023, 4:34am UTC](https://community.freefem.org/t/symmetric-boundary-condition-not-satisfied/2527 "2023-06-10T04:34:40Z")
Dear all! I’m solving a chemical problem like this. And this is my edp code: test.edp (1.8 KB) I try to compute half of the domain. dx(ci)=0 should be satisfied at left boundary, but it seems to be wrong. I’m no… --- ## [Split a mesh by adding a node at the barycenter of elements](https://community.freefem.org/t/split-a-mesh-by-adding-a-node-at-the-barycenter-of-elements/2533)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 4\ **Last updated:** [June 9, 2023, 4:43pm UTC](https://community.freefem.org/t/split-a-mesh-by-adding-a-node-at-the-barycenter-of-elements/2533 "2023-06-09T16:43:51Z")
Hello all, Given a 2D mesh Th .msh, what is the more efficient way to split the mesh by adding one node at the barycenter and then link the vertices of the triangles to the new nodes ? Thank you in advance, Best regar… --- ## [MPI test for script in (examples/mpi)](https://community.freefem.org/t/mpi-test-for-script-in-examples-mpi/2526)
**Author:** [@Alexis\_He](https://community.freefem.org/u/Alexis_He)\ **Replies:** 9\ **Last updated:** [June 8, 2023, 5:21am UTC](https://community.freefem.org/t/mpi-test-for-script-in-examples-mpi/2526 "2023-06-08T05:21:50Z")
Hello everyone. I’m not sure why all of scripts which need load "MUMPS\_mpi" should be run with using the sudo command Env : ubuntu22.04 with FreeFem++ compiled using mpich2 Installation information : ./configure --en… --- ## [Segault in ffglut with fill =0](https://community.freefem.org/t/segault-in-ffglut-with-fill-0/2529)
**Author:** [@marchywka](https://community.freefem.org/u/marchywka)\ **Replies:** 1\ **Last updated:** [June 7, 2023, 8:15pm UTC](https://community.freefem.org/t/segault-in-ffglut-with-fill-0/2529 "2023-06-07T20:15:27Z")
This example seems to capture the problem and likely is reproducble. Hitting return on the first plot causes a segfault as the attempt to draw the “fill=0” fails, 1 : mesh Th = square(100,100); 2 : fespace Vh(… --- ## [How to work with regions on imported meshes (Gmsh)](https://community.freefem.org/t/how-to-work-with-regions-on-imported-meshes-gmsh/2523)
**Author:** [@m.lbolok](https://community.freefem.org/u/m.lbolok)\ **Replies:** 1\ **Last updated:** [June 7, 2023, 3:24pm UTC](https://community.freefem.org/t/how-to-work-with-regions-on-imported-meshes-gmsh/2523 "2023-06-07T15:24:52Z")
Hi, To define regions, I create them separately in a cad tool and mesh them in the Gmsh. By importing the mesh into FreeFem, I can distinguish the regions but FreeFem does not consider a unified domain and solve just on… --- ## [Read or write a file backwards](https://community.freefem.org/t/read-or-write-a-file-backwards/2522)
**Author:** [@lassounon](https://community.freefem.org/u/lassounon)\ **Replies:** 0\ **Last updated:** [June 6, 2023, 12:10pm UTC](https://community.freefem.org/t/read-or-write-a-file-backwards/2522 "2023-06-06T12:10:09Z")
Hello everyone. I saved a “u” file where u is the solution of an evolution equation in the form: x.y.u(x,y) at each iteration of time t of t=0, x.y.u(x,y)… at t=1, x.y.u(x,y). I would like to know how to create anot… --- ## [Usage of MatNullSpace](https://community.freefem.org/t/usage-of-matnullspace/2518)
**Author:** [@cmd](https://community.freefem.org/u/cmd)\ **Replies:** 6\ **Last updated:** [June 5, 2023, 12:37pm UTC](https://community.freefem.org/t/usage-of-matnullspace/2518 "2023-06-05T12:37:58Z")
Hello, I am having convergence issues solving a nearly singular system using a KSP object with -pc\_type lu. From the PETSc documentation, I understand that adding a nullspace constraint using MatNullSpace might help solv… --- ## [Comment corriger ceci?](https://community.freefem.org/t/comment-corriger-ceci/2520)
**Author:** [@aweni](https://community.freefem.org/u/aweni)\ **Replies:** 0\ **Last updated:** [June 5, 2023, 10:50am UTC](https://community.freefem.org/t/comment-corriger-ceci/2520 "2023-06-05T10:50:09Z")
current line = 84 Internal error : Methode de Galerkine (a faire) line :4803, in file problem.cpp Internal error : Methode de Galerkine (a faire) line :4803, in file problem.cpp err code 6 , mpirank 0 FreeFem++ … --- ## [BDM1 face element](https://community.freefem.org/t/bdm1-face-element/1397)
**Author:** [@candy](https://community.freefem.org/u/candy)\ **Replies:** 3\ **Last updated:** [June 2, 2023, 9:52am UTC](https://community.freefem.org/t/bdm1-face-element/1397 "2023-06-02T09:52:47Z")
Hello, I am studying high order FEMs for Maxwell problems. And I want to use BDM1 face element in 3D, I hope FreeFEM++ can include this element. --- ## [Implement spring elements](https://community.freefem.org/t/implement-spring-elements/2513)
**Author:** [@arallu](https://community.freefem.org/u/arallu)\ **Replies:** 3\ **Last updated:** [June 1, 2023, 5:00pm UTC](https://community.freefem.org/t/implement-spring-elements/2513 "2023-06-01T17:00:15Z")
Hello, What would be the best way to add ideal springs on a continuous media (a beam for example)? A solution could be to modify one matrix corresponding to the weak formulation, but it seems to be not so easy (I must k… --- ## [Three-dimensional BDM element in Freefem](https://community.freefem.org/t/three-dimensional-bdm-element-in-freefem/2515)
**Author:** [@junjie](https://community.freefem.org/u/junjie)\ **Replies:** 0\ **Last updated:** [June 1, 2023, 1:58pm UTC](https://community.freefem.org/t/three-dimensional-bdm-element-in-freefem/2515 "2023-06-01T13:58:07Z")
Hello everyone. Is there a three-dimensional BDM element in Freefem? If so, how can I use it？ --- ## [Movemesh23 for meshS](https://community.freefem.org/t/movemesh23-for-meshs/2511)
**Author:** [@alfat](https://community.freefem.org/u/alfat)\ **Replies:** 0\ **Last updated:** [May 31, 2023, 5:05am UTC](https://community.freefem.org/t/movemesh23-for-meshs/2511 "2023-05-31T05:05:57Z")
Hi all, I am trying to simulate crack propagation in Thin Layer using FreeFEM++. I use the command movemesh23 mesh th = square(n, n, \[-1\*L0+(L0+L0)\*x, -1\*h0+(h0+h0)\*y\],flags=1); meshS Th=movemesh23(th,transfo=\[x,y,z\])… --- ## [3d labels questions](https://community.freefem.org/t/3d-labels-questions/2492)
**Author:** [@YAOH](https://community.freefem.org/u/YAOH)\ **Replies:** 2\ **Last updated:** [May 30, 2023, 12:36pm UTC](https://community.freefem.org/t/3d-labels-questions/2492 "2023-05-30T12:36:14Z")
Hi all, I have a 3D mesh which is a cubic but with some cylinders borders inside. First I build a 2D square mesh with some circles, I put label = 1,2,3,4 for square’s borders, respectively. label = 5 for circles. The … --- ## [Meshing with acute-angled triangles](https://community.freefem.org/t/meshing-with-acute-angled-triangles/2392)
**Author:** [@AbuAzzan](https://community.freefem.org/u/AbuAzzan)\ **Replies:** 16\ **Last updated:** [May 30, 2023, 8:25am UTC](https://community.freefem.org/t/meshing-with-acute-angled-triangles/2392 "2023-05-30T08:25:49Z")
Hi, Is there a command in FreeFem++ to build a meshing with “only acute angles” for all elements?. Let us say the constructed triangles are equilateral as an example. I did not find that in the documentation. Can someon… --- ## [PETSc error of ChangeNumbering](https://community.freefem.org/t/petsc-error-of-changenumbering/2509)
**Author:** [@yhao](https://community.freefem.org/u/yhao)\ **Replies:** 2\ **Last updated:** [May 29, 2023, 6:08pm UTC](https://community.freefem.org/t/petsc-error-of-changenumbering/2509 "2023-05-29T18:08:20Z")
Hi, I am working on 3D Navier Stokes equations. I use Newton’s method. We met an error when executing ChangeNumbering from Freefem to PETSc: Assertion fail : (ptIn-\>N() == ptA-\>\_A-\>getDof()) line :2946, in file PETSc-… --- ## [Space of weak functions](https://community.freefem.org/t/space-of-weak-functions/2507)
**Author:** [@freefemuser](https://community.freefem.org/u/freefemuser)\ **Replies:** 1\ **Last updated:** [May 29, 2023, 3:46pm UTC](https://community.freefem.org/t/space-of-weak-functions/2507 "2023-05-29T15:46:32Z")
fespace Wh1(Th, P0); fespace Wh2(Th, P0); Is there any direct command in freefem++ to define the space of discrete weak functions. Thanks in advance. --- ## [Taille d'un vecteur solution](https://community.freefem.org/t/taille-dun-vecteur-solution/2503)
**Author:** [@Leonidas](https://community.freefem.org/u/Leonidas)\ **Replies:** 1\ **Last updated:** [May 29, 2023, 3:38pm UTC](https://community.freefem.org/t/taille-dun-vecteur-solution/2503 "2023-05-29T15:38:06Z")
Bonjour, sur Freefem on définit un maillage, on définit l’espace d’approximation discret et on résoud un problème sur cet espace pour obtenir une certaine solution “u”. J’aimerai savoir comment connaissant cette solutio… --- ## [Pas du maillage dans Freefem](https://community.freefem.org/t/pas-du-maillage-dans-freefem/2500)
**Author:** [@Leonidas](https://community.freefem.org/u/Leonidas)\ **Replies:** 3\ **Last updated:** [May 29, 2023, 3:15pm UTC](https://community.freefem.org/t/pas-du-maillage-dans-freefem/2500 "2023-05-29T15:15:14Z")
Bonjour, Freefem génére un maillage connaissant le nombre de nœuds au bords du domaine basé sur l’algorithme de Delaunay-Voronoi Par exemple la commande int n=50; mesh Th=square(n,n,\[x,y\]); Et une fois le maillage gé… --- ## [Appel d'une solution obtenue dans Freefem dans un autre code Freefem](https://community.freefem.org/t/appel-dune-solution-obtenue-dans-freefem-dans-un-autre-code-freefem/2494)
**Author:** [@Leonidas](https://community.freefem.org/u/Leonidas)\ **Replies:** 4\ **Last updated:** [May 29, 2023, 7:35am UTC](https://community.freefem.org/t/appel-dune-solution-obtenue-dans-freefem-dans-un-autre-code-freefem/2494 "2023-05-29T07:35:15Z")
Bonjour, j’ai résolu un problème d’EDP évolutive sur Freefem et ça marche bien. Le problème que je rencontre est le suivant : comment sauvegarder la solution que j’ai obtenu et également comment l’appeler (cette solutio… --- ## [Unaffected Results with Parameter](https://community.freefem.org/t/unaffected-results-with-parameter/2497)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 6\ **Last updated:** [May 28, 2023, 2:36am UTC](https://community.freefem.org/t/unaffected-results-with-parameter/2497 "2023-05-28T02:36:28Z")
Hello , I am surprised by the results of my 3d model. Its results remain unaffected for all values of parameters used in the model. \[@prj @frederichecht \] can anyone suggest/comment to resolve it? =================… --- ## [String access in FreeFem++](https://community.freefem.org/t/string-access-in-freefem/2498)
**Author:** [@galfras](https://community.freefem.org/u/galfras)\ **Replies:** 4\ **Last updated:** [May 27, 2023, 11:22am UTC](https://community.freefem.org/t/string-access-in-freefem/2498 "2023-05-27T11:22:29Z")
Hello! Is it possible to access strings in FreeFem++? I am trying to replace specific letters in a string and I don’t know how to do it. This is the idea of the code (fn is the string): for(int i = 0; i\ **Author:** [@abanderam](https://community.freefem.org/u/abanderam)\ **Replies:** 5\ **Last updated:** [May 26, 2023, 1:42pm UTC](https://community.freefem.org/t/dfft-not-working-as-spected/2491 "2023-05-26T13:42:33Z") I am trying to obtain the discrete fourier transform of a function in an unit square, but the results i obtain with dfft package are different with the ones that I obtain using a Vandermode matrix. I provide a minimal co… --- ## [Changing the orientation of 3d mesh](https://community.freefem.org/t/changing-the-orientation-of-3d-mesh/2490)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 0\ **Last updated:** [May 25, 2023, 5:33am UTC](https://community.freefem.org/t/changing-the-orientation-of-3d-mesh/2490 "2023-05-25T05:33:14Z")
Hello Everyone, I have generated a T-shaped domain (3D) using “buildlayer” command for 2d domain (T). Now, the 2d domain extended along z direction \[ 0 to 1\] which changes the orientation of 3d domain. I wish to rotat… --- ## [Doubt in the variational formulation of LaplaceRT.edp](https://community.freefem.org/t/doubt-in-the-variational-formulation-of-laplacert-edp/2471)
**Author:** [@89273166](https://community.freefem.org/u/89273166)\ **Replies:** 5\ **Last updated:** [May 24, 2023, 7:39am UTC](https://community.freefem.org/t/doubt-in-the-variational-formulation-of-laplacert-edp/2471 "2023-05-24T07:39:06Z")
This code is to find the finite element solution for the mixed formulation for the poission equation(please refer to page no. 540 for details). In the above code how to find the first term " pq1e^-15". Thank you in … --- ## [Assertion fail: (kkk++\<10)](https://community.freefem.org/t/assertion-fail-kkk-10/2485)
**Author:** [@forgotthesemicolon](https://community.freefem.org/u/forgotthesemicolon)\ **Replies:** 0\ **Last updated:** [May 23, 2023, 5:14am UTC](https://community.freefem.org/t/assertion-fail-kkk-10/2485 "2023-05-23T05:14:06Z")
Hi everyone, I have a code where I have to make a mesh with periodic conditions for some sufaces with various number of sides and while it works for surfaces with 8 sides, for more sides I just keep getting this error :… --- ## [Interpolation operator "="](https://community.freefem.org/t/interpolation-operator/2476)
**Author:** [@kallol](https://community.freefem.org/u/kallol)\ **Replies:** 4\ **Last updated:** [May 21, 2023, 1:29pm UTC](https://community.freefem.org/t/interpolation-operator/2476 "2023-05-21T13:29:23Z")
Dear all, I want to interpolate a function u from one finite element space Vh to another finite element space Wh. Both spaces are based on P2 dicontinuous finite elements. I have used the operator “=” for interpolation.… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=30) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=32)