# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=21 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 22 --- ## [Calculating the maximum and minimum values of the difference between two consecutive iterations](https://community.freefem.org/t/calculating-the-maximum-and-minimum-values-of-the-difference-between-two-consecutive-iterations/3060)
**Author:** [@AbuAzzan](https://community.freefem.org/u/AbuAzzan)\ **Replies:** 6\ **Last updated:** [April 6, 2024, 7:31am UTC](https://community.freefem.org/t/calculating-the-maximum-and-minimum-values-of-the-difference-between-two-consecutive-iterations/3060 "2024-04-06T07:31:20Z")
Hi community My problem is to find the extreme values of the difference between two consecutive iterations u^{n+1}\_{ih\_i} and u^{n}\_{ih\_i} of a Schwarz algorithm. For a certain purpose, this is done by excluding the val… --- ## [The mesh file doesn't contain vertices in FreeFEM](https://community.freefem.org/t/the-mesh-file-doesnt-contain-vertices-in-freefem/3069)
**Author:** [@dominiquebodin](https://community.freefem.org/u/dominiquebodin)\ **Replies:** 7\ **Last updated:** [April 1, 2024, 2:29pm UTC](https://community.freefem.org/t/the-mesh-file-doesnt-contain-vertices-in-freefem/3069 "2024-04-01T14:29:20Z")
Hello FreeFEM community, I used Gmsh to generate a 3D mesh. By the fact, the Gmsh code is extracted from a Gmsh tutorial (t19.geo). Unfortunately I got the following error when reading the mesh with FreeFEM: ERROR: Th… --- ## [DG method and PETSc](https://community.freefem.org/t/dg-method-and-petsc/3077)
**Author:** [@111-1111](https://community.freefem.org/u/111-1111)\ **Replies:** 4\ **Last updated:** [March 31, 2024, 2:51pm UTC](https://community.freefem.org/t/dg-method-and-petsc/3077 "2024-03-31T14:51:05Z")
Dear PETSc developer, the problem I am solving may involve the DG finite element method to handle complex fluid problems in porous media. May I ask if PETSc supports the parallelism of the DG finite element method. --- ## [SLEPc: EPSSolve ERROR](https://community.freefem.org/t/slepc-epssolve-error/2887)
**Author:** [@WeiQLiu](https://community.freefem.org/u/WeiQLiu)\ **Replies:** 7\ **Last updated:** [March 28, 2024, 9:17am UTC](https://community.freefem.org/t/slepc-epssolve-error/2887 "2024-03-28T09:17:20Z")
Dear all, I’m currently reproducing a paper: Sabino et.al 2020. It’s background in physics is the vortex-induced vibration of a spring-mounted, damped, rigid circular cylinder, immersed in a Newtonian viscous flow and c… --- ## [Problem imposing tangent stress condition](https://community.freefem.org/t/problem-imposing-tangent-stress-condition/3065)
**Author:** [@ilavi](https://community.freefem.org/u/ilavi)\ **Replies:** 4\ **Last updated:** [March 26, 2024, 6:19pm UTC](https://community.freefem.org/t/problem-imposing-tangent-stress-condition/3065 "2024-03-26T18:19:08Z")
Hi, I am solving a compressible Stokes problem with a prescribed pressure on a hexagon with the following BCs on each face i: u.ni =0 ti.(sigma.ni) = gi But in my scheme the 2nd condition is not imposed to a satisfac… --- ## [VDW diffusion interface model](https://community.freefem.org/t/vdw-diffusion-interface-model/3064)
**Author:** [@111-1111](https://community.freefem.org/u/111-1111)\ **Replies:** 0\ **Last updated:** [March 25, 2024, 8:26am UTC](https://community.freefem.org/t/vdw-diffusion-interface-model/3064 "2024-03-25T08:26:52Z")
Hello developer, I am a beginner about this software.I encountered difficulties in solving the following problem The code is as follows func u0=0; func v0=0; real rhol=1.46,rhog=0.58,delta=0.05; func rho0=0.5\*(rho… --- ## [Can someone tell me how to reset the finite element space](https://community.freefem.org/t/can-someone-tell-me-how-to-reset-the-finite-element-space/3062)
**Author:** [@gdxaa](https://community.freefem.org/u/gdxaa)\ **Replies:** 0\ **Last updated:** [March 25, 2024, 2:57am UTC](https://community.freefem.org/t/can-someone-tell-me-how-to-reset-the-finite-element-space/3062 "2024-03-25T02:57:28Z")
I’m doing a finite element simulation，I wanna use for circle to collect some data，but I dont know how to reset the finite element space at the start of for circle my code just like fespace Vh（Th，P1） for（）{ } --- ## [Lagrange multiplier applied to functions in different FE spaces](https://community.freefem.org/t/lagrange-multiplier-applied-to-functions-in-different-fe-spaces/3059)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 3\ **Last updated:** [March 23, 2024, 6:07pm UTC](https://community.freefem.org/t/lagrange-multiplier-applied-to-functions-in-different-fe-spaces/3059 "2024-03-23T18:07:23Z")
Say, mesh Th = (solid + fluid) regions ; //This mesh will be updated mesh Thf = trunc(Th, region==fluid); //This is the fluid mesh which will be updated consequently mesh Ths = trunc(Th, region==solid); //Solid mesh, bu… --- ## [Current Extraction for each node over time steps](https://community.freefem.org/t/current-extraction-for-each-node-over-time-steps/2963)
**Author:** [@MehranK1](https://community.freefem.org/u/MehranK1)\ **Replies:** 2\ **Last updated:** [February 14, 2024, 8:49pm UTC](https://community.freefem.org/t/current-extraction-for-each-node-over-time-steps/2963 "2024-02-14T20:49:44Z")
Hello, I have a code for electromagnetics simulation and analysis in FreeFem over a time period. I need to extract three different files. One is a file that contains all the coordinates, the second one is the indices of… --- ## [Fespaces in vectorized formulation](https://community.freefem.org/t/fespaces-in-vectorized-formulation/3055)
**Author:** [@m.lbolok](https://community.freefem.org/u/m.lbolok)\ **Replies:** 1\ **Last updated:** [March 21, 2024, 5:39pm UTC](https://community.freefem.org/t/fespaces-in-vectorized-formulation/3055 "2024-03-21T17:39:08Z")
Hi, Is it correct to have different fespaces and solve a vectorized equation as: fespace Vh(Omega, P2); fespace Ph(Omega, P1); Vh wr,wz,urs,uzs; Ph hs,q; problem Myproblem(\[hs,urs,uzs\],\[q,wr,wz\]) =int2d(Omega)((y\*… --- ## [Normal boundary condition](https://community.freefem.org/t/normal-boundary-condition/341)
**Author:** [@michaellevitin](https://community.freefem.org/u/michaellevitin)\ **Replies:** 11\ **Last updated:** [March 20, 2024, 11:27am UTC](https://community.freefem.org/t/normal-boundary-condition/341 "2024-03-20T11:27:05Z")
When solving some (vector) BVP for 2d elasticity, I’d like to specify a Dirichlet boundary condition for the normal component of a vector field \[u,v\], as, say, …+on(1, u\*N.x+v\*N.y=0). I understand that the syntax of on … --- ## [3D mesh: periodic boundary conditions and unstructured mesh](https://community.freefem.org/t/3d-mesh-periodic-boundary-conditions-and-unstructured-mesh/2781)
**Author:** [@jsmacd](https://community.freefem.org/u/jsmacd)\ **Replies:** 6\ **Last updated:** [March 19, 2024, 9:56pm UTC](https://community.freefem.org/t/3d-mesh-periodic-boundary-conditions-and-unstructured-mesh/2781 "2024-03-19T21:56:52Z")
Dear Community, I understand that the faces have to be the same for periodic boundary conditions, but I also would like to use an unstructured mesh. Does anyone know how I can accomplish this? The code below is what doe… --- ## [Resolve an hyperbolic system with FF++](https://community.freefem.org/t/resolve-an-hyperbolic-system-with-ff/3047)
**Author:** [@Gigi](https://community.freefem.org/u/Gigi)\ **Replies:** 1\ **Last updated:** [March 18, 2024, 12:32pm UTC](https://community.freefem.org/t/resolve-an-hyperbolic-system-with-ff/3047 "2024-03-18T12:32:49Z")
Hi, please, how we cal write with FF++, the variational formulation of the following hyperbolic system: \\tau\*\\dfrac{\\partial q}{\\partial t}= -q - D\* \\dfrac{\\partial V}{\\partial x}, \\dfrac{\\partial V}{\\partial t}=- \\… --- ## [Minimum/maximum edge length of the mesh in the entire domain](https://community.freefem.org/t/minimum-maximum-edge-length-of-the-mesh-in-the-entire-domain/731)
**Author:** [@hezl09](https://community.freefem.org/u/hezl09)\ **Replies:** 2\ **Last updated:** [March 17, 2024, 9:28pm UTC](https://community.freefem.org/t/minimum-maximum-edge-length-of-the-mesh-in-the-entire-domain/731 "2024-03-17T21:28:59Z")
Hi everyone, I need help from you. I’m trying to find the minimum/maximum edge length of the mesh in the entire domain. I tried the following two options but neither of them worked well for my test case, see the figure b… --- ## [The example in FreeFem Documentation about Neo-Hookean Compressible Material](https://community.freefem.org/t/the-example-in-freefem-documentation-about-neo-hookean-compressible-material/3044)
**Author:** [@NYKong](https://community.freefem.org/u/NYKong)\ **Replies:** 1\ **Last updated:** [March 17, 2024, 4:34pm UTC](https://community.freefem.org/t/the-example-in-freefem-documentation-about-neo-hookean-compressible-material/3044 "2024-03-17T16:34:58Z")
Hi , the problem is that the program is misbehaved in the official FreeFem-Document (page 636), which is an example about a Neo-Hookean Compressible Material. I meet errors in line 9 and other definitions of macro. The w… --- ## [Hyperbolic problem with FF++](https://community.freefem.org/t/hyperbolic-problem-with-ff/3043)
**Author:** [@Gigi](https://community.freefem.org/u/Gigi)\ **Replies:** 1\ **Last updated:** [March 17, 2024, 12:14pm UTC](https://community.freefem.org/t/hyperbolic-problem-with-ff/3043 "2024-03-17T12:14:07Z")
Hi, i try to write a FF++ code to resolve attached problem I write the following code but it give me a false value (the values of solution must be positives and with my code, the solutions are negatives. Thank you … --- ## [How to input the modulus of gradients](https://community.freefem.org/t/how-to-input-the-modulus-of-gradients/3046)
**Author:** [@zxy](https://community.freefem.org/u/zxy)\ **Replies:** 1\ **Last updated:** [March 17, 2024, 10:49am UTC](https://community.freefem.org/t/how-to-input-the-modulus-of-gradients/3046 "2024-03-17T10:49:55Z")
Hi, I want to write it: I code as: macro msquare(u) (dx(u)^2+dy(u)^2)// mesh Th = buildmesh(c1(10)+c2(10)+c3(10)+c4(10)); fespace Vh(Th,P1); Vh u,w,oldu,q,f; Vh v,oldv; problem fcv(\[u,v\],\[w,q\])= -int2d(Th)(v… --- ## [Division issue on plot due to mesh?](https://community.freefem.org/t/division-issue-on-plot-due-to-mesh/3045)
**Author:** [@Wilkinsonad01](https://community.freefem.org/u/Wilkinsonad01)\ **Replies:** 0\ **Last updated:** [March 16, 2024, 5:23pm UTC](https://community.freefem.org/t/division-issue-on-plot-due-to-mesh/3045 "2024-03-16T17:23:30Z")
Hi, I came a cross an issue plotting the f(x,y) = (x^2+y^2)/N where N is a real number when using the code below the plots looked correct: mesh Th = square(10,10); plot(Th, wait = true); fespace U(Th, P1); U u; u… --- ## [How to get more exact solution of 3D Schrodinger equation](https://community.freefem.org/t/how-to-get-more-exact-solution-of-3d-schrodinger-equation/1842)
**Author:** [@kilasuelika](https://community.freefem.org/u/kilasuelika)\ **Replies:** 14\ **Last updated:** [March 15, 2024, 4:13pm UTC](https://community.freefem.org/t/how-to-get-more-exact-solution-of-3d-schrodinger-equation/1842 "2024-03-15T16:13:27Z")
I use following code to solve 3D Schrodinger equation of Hydrogen atom. real me=9.10938356e-31; real planckh=6.62607004e-34; real hbar=1.0545718e-34; real kgm2Ds2ToeV=6.24150636309e18; real a0=5.2917721039e-11;//bohr ra… --- ## [Degrees of freedom](https://community.freefem.org/t/degrees-of-freedom/3041)
**Author:** [@junjie](https://community.freefem.org/u/junjie)\ **Replies:** 2\ **Last updated:** [March 15, 2024, 11:29am UTC](https://community.freefem.org/t/degrees-of-freedom/3041 "2024-03-15T11:29:04Z")
Is it possible to derive the degrees of freedom of the unknowns in the finite element space in the dissected region in Freefem? If so, how do I implement it? Thank you very much! --- ## [Adaptmesh in 1D, for a segment](https://community.freefem.org/t/adaptmesh-in-1d-for-a-segment/3010)
**Author:** [@tess35](https://community.freefem.org/u/tess35)\ **Replies:** 5\ **Last updated:** [March 14, 2024, 4:04pm UTC](https://community.freefem.org/t/adaptmesh-in-1d-for-a-segment/3010 "2024-03-14T16:04:59Z")
Hi, Could you remind me how to adaptmesh for 1D mesh ? Thank --- ## [Defining multiple local meshes using buildDmesh](https://community.freefem.org/t/defining-multiple-local-meshes-using-builddmesh/949)
**Author:** [@KBarrett](https://community.freefem.org/u/KBarrett)\ **Replies:** 12\ **Last updated:** [March 14, 2024, 3:27pm UTC](https://community.freefem.org/t/defining-multiple-local-meshes-using-builddmesh/949 "2024-03-14T15:27:54Z")
Hello all, I am using the macro\_ddm.idp to use buildDmesh and createMat with macro def(i) \[i, i#B, i#C\] // to solve the 3D elasticity equation in parallel using PETSc. I also need to solve a 1D and 2D varf in the same p… --- ## [Error reading gmsh file](https://community.freefem.org/t/error-reading-gmsh-file/3035)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 7\ **Last updated:** [March 14, 2024, 12:48pm UTC](https://community.freefem.org/t/error-reading-gmsh-file/3035 "2024-03-14T12:48:46Z")
Hello, I’m trying to read a msh file and I’m getting the following error SetOfEdges4::add overflow de la pile 24 24 Fatal error in the mesh generator 888 current line = 34 Meshing error: Bamg number : 888, Meshin… --- ## [A problem about the coordinate singularity at r=0 for axisymmetric problme](https://community.freefem.org/t/a-problem-about-the-coordinate-singularity-at-r-0-for-axisymmetric-problme/3034)
**Author:** [@clthu](https://community.freefem.org/u/clthu)\ **Replies:** 3\ **Last updated:** [March 13, 2024, 11:39am UTC](https://community.freefem.org/t/a-problem-about-the-coordinate-singularity-at-r-0-for-axisymmetric-problme/3034 "2024-03-13T11:39:35Z")
Dear all, These days I meet a problem about the axisymmetric NS equations. I solve \[u,p\] with test function\[v,phi\] and when I wrote the weak form I found a problem, for example the term of pressure gradient on the righ… --- ## [Fisher's Equation](https://community.freefem.org/t/fishers-equation/3033)
**Author:** [@Wilkinsonad01](https://community.freefem.org/u/Wilkinsonad01)\ **Replies:** 1\ **Last updated:** [March 13, 2024, 8:34am UTC](https://community.freefem.org/t/fishers-equation/3033 "2024-03-13T08:34:53Z")
Is there an example of using FreeFEM to solve Fisher’s equation? thanks --- ## [Logarithm Error in system of PDEs](https://community.freefem.org/t/logarithm-error-in-system-of-pdes/3027)
**Author:** [@Wilkinsonad01](https://community.freefem.org/u/Wilkinsonad01)\ **Replies:** 5\ **Last updated:** [March 12, 2024, 9:31pm UTC](https://community.freefem.org/t/logarithm-error-in-system-of-pdes/3027 "2024-03-12T21:31:59Z")
Hi, I am very new to FreeFEM so I am probably making a few simple mistakes but would really appreciate your help. I am trying to solve a system of 6 PDEs to model cancer growth. This is my code so far: real L = 1.0; … --- ## [Error during matrix-vector multiplication with ffddm](https://community.freefem.org/t/error-during-matrix-vector-multiplication-with-ffddm/3030)
**Author:** [@luyu](https://community.freefem.org/u/luyu)\ **Replies:** 2\ **Last updated:** [March 12, 2024, 9:29am UTC](https://community.freefem.org/t/error-during-matrix-vector-multiplication-with-ffddm/3030 "2024-03-12T09:29:19Z")
Using ffddm, following the example Maxwell-3d-simple.edp in the examples/ffddm folder, I am trying to see what each operation does by printing out the results. So here I am multiplying the partition of unity matrix pr#D… --- ## [Difference in mesh format between 2D and 3D](https://community.freefem.org/t/difference-in-mesh-format-between-2d-and-3d/3019)
**Author:** [@smyrback](https://community.freefem.org/u/smyrback)\ **Replies:** 1\ **Last updated:** [March 11, 2024, 8:50pm UTC](https://community.freefem.org/t/difference-in-mesh-format-between-2d-and-3d/3019 "2024-03-11T20:50:24Z")
Hi, I’m using a C++ library that is built on top of FreeFem source code. When importing meshes from files, it requires the format generated by e.g. the following FreeFem code snippet: mesh Th square(5,5); savemesh(Th,… --- ## [Vectorial solution of Laplace using varf](https://community.freefem.org/t/vectorial-solution-of-laplace-using-varf/3025)
**Author:** [@PoTS](https://community.freefem.org/u/PoTS)\ **Replies:** 2\ **Last updated:** [March 11, 2024, 8:46pm UTC](https://community.freefem.org/t/vectorial-solution-of-laplace-using-varf/3025 "2024-03-11T20:46:22Z")
Hello, dear participants. I solve the problem of elasticity in 2D using varf. I get the solution as a vector \[u1,u2\]. Is it possible to get directly the arrays u1 and u2 separately using some command in FreeFem++? --- ## [Error reading file in triangulate](https://community.freefem.org/t/error-reading-file-in-triangulate/3021)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 2\ **Last updated:** [March 11, 2024, 3:01pm UTC](https://community.freefem.org/t/error-reading-file-in-triangulate/3021 "2024-03-11T15:01:23Z")
Hello, I’m trying to read a file to use in triangulate but I’m getting the following error: we read 6 coordinates xy we build 6 boundary edges we read 6 coordinates xy current line = 320 Assertion fail : (ar… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=20) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=22)