# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=25 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 26 --- ## [A problem about 3D mesh generation](https://community.freefem.org/t/a-problem-about-3d-mesh-generation/1821)
**Author:** [@RYP](https://community.freefem.org/u/RYP)\ **Replies:** 7\ **Last updated:** [December 18, 2023, 10:00am UTC](https://community.freefem.org/t/a-problem-about-3d-mesh-generation/1821 "2023-12-18T10:00:54Z")
Hi,everyone, I have a question about tetgreconstruction. I give two files as follows, The difference between them is only the parameter hsize. However, test2.edp gives a wrong result. I’m confused about this. Thank you… --- ## [How do I obtain the matrix ordering of the boundaries?](https://community.freefem.org/t/how-do-i-obtain-the-matrix-ordering-of-the-boundaries/2834)
**Author:** [@ksugahar](https://community.freefem.org/u/ksugahar)\ **Replies:** 1\ **Last updated:** [December 18, 2023, 9:50am UTC](https://community.freefem.org/t/how-do-i-obtain-the-matrix-ordering-of-the-boundaries/2834 "2023-12-18T09:50:26Z")
How do I obtain the matrix ordering number of the boundary nodes? In the following example I have generated a hexagonal mesh and six boundary nodes. I want to obtain \[1,4 0, 6, 5, 2\] as an array. I might be able to de… --- ## [Biharmonic equation with only zero normal derivative](https://community.freefem.org/t/biharmonic-equation-with-only-zero-normal-derivative/2835)
**Author:** [@jvellojin](https://community.freefem.org/u/jvellojin)\ **Replies:** 1\ **Last updated:** [December 15, 2023, 12:11pm UTC](https://community.freefem.org/t/biharmonic-equation-with-only-zero-normal-derivative/2835 "2023-12-15T12:11:01Z")
Dear Freefem community, I’m trying to manipulate the boundary conditions for the bilaplacian problem, like the code below. load "Morley" // Parameters int nn = 10; real h = 0.01; real f = 1; // Mesh mesh Th = square(nn… --- ## [Adaptmesh with a posteriori error](https://community.freefem.org/t/adaptmesh-with-a-posteriori-error/2833)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 1\ **Last updated:** [December 13, 2023, 2:41pm UTC](https://community.freefem.org/t/adaptmesh-with-a-posteriori-error/2833 "2023-12-13T14:41:10Z")
Hey everyone, I’m trying to adapt a mesh regarding the a posteriori error but it seems the mesh is no refined. Could someone tell me what I did wrong in this code //RHS func f = 8\*pi\*pi\*sin(2\*pi\*x)\*sin(2\*pi\*y); //exac… --- ## [Edge to element](https://community.freefem.org/t/edge-to-element/2825)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 3\ **Last updated:** [December 12, 2023, 2:47pm UTC](https://community.freefem.org/t/edge-to-element/2825 "2023-12-12T14:47:48Z")
Hello everyone, how do I create an edge to element matrix using FreeFem++? So, basically, given the edge number, I would like to know the elements that share that edge. Is it possible? --- ## [Maximal colors scale of the isovalues](https://community.freefem.org/t/maximal-colors-scale-of-the-isovalues/2832)
**Author:** [@lassounon](https://community.freefem.org/u/lassounon)\ **Replies:** 2\ **Last updated:** [December 12, 2023, 2:10pm UTC](https://community.freefem.org/t/maximal-colors-scale-of-the-isovalues/2832 "2023-12-12T14:10:28Z")
Hello everyone. I defined a color scale in my freefem code (“from the zone with zero saturation in blue to the zone with high saturation in red”), but at the output on the image the iso-value in the red zone is almost z… --- ## [Mesh in polar coordinates](https://community.freefem.org/t/mesh-in-polar-coordinates/2738)
**Author:** [@RaghunathBandha](https://community.freefem.org/u/RaghunathBandha)\ **Replies:** 6\ **Last updated:** [December 11, 2023, 2:22am UTC](https://community.freefem.org/t/mesh-in-polar-coordinates/2738 "2023-12-11T02:22:28Z")
Suppose we have a domain in polar coordinates with boundary r=f(theta). 0\<=theta\<=2\*pi. How to build a mesh in FreeFem++. Can I use movemesh in polar to polar transformation from (r , theta) coordinates to (r’ , theta’) … --- ## [Vector deduplication operation](https://community.freefem.org/t/vector-deduplication-operation/2829)
**Author:** [@Tan](https://community.freefem.org/u/Tan)\ **Replies:** 2\ **Last updated:** [December 11, 2023, 11:03am UTC](https://community.freefem.org/t/vector-deduplication-operation/2829 "2023-12-11T11:03:37Z")
Hello, I would like to ask how to operate vector deduplication in FreeFem? For example, I have a vector, but there are many repeated elements in it. I need to remove the repeated elements and save them in a new vector. D… --- ## [Importing Mesh Issue with Orientation](https://community.freefem.org/t/importing-mesh-issue-with-orientation/2826)
**Author:** [@FluidMan](https://community.freefem.org/u/FluidMan)\ **Replies:** 2\ **Last updated:** [December 10, 2023, 8:47pm UTC](https://community.freefem.org/t/importing-mesh-issue-with-orientation/2826 "2023-12-10T20:47:21Z")
Hi everyone, I am getting this error when I import my mesh from gmsh and I can’t figure out how to address it. Any explanations or direction would be appreciated! with code: load "msh3" verbosity=1; mesh3 Th("Attempt2… --- ## [Help Making Sketched Geometry](https://community.freefem.org/t/help-making-sketched-geometry/2814)
**Author:** [@FluidMan](https://community.freefem.org/u/FluidMan)\ **Replies:** 6\ **Last updated:** [December 8, 2023, 4:16pm UTC](https://community.freefem.org/t/help-making-sketched-geometry/2814 "2023-12-08T16:16:59Z")
Hi everyone, I cannot think of a clever way to make this domain (Picture attached) in FreeFem. Any thoughts or ideas? The domain is 1+1/8 in length, 1 height, and 1 width. There is a 1/4 depth and 1/8 wide channel that … --- ## [How to implement normalization Constraint and Single Value variable in Parallel Setting?](https://community.freefem.org/t/how-to-implement-normalization-constraint-and-single-value-variable-in-parallel-setting/2824)
**Author:** [@xuanshi123](https://community.freefem.org/u/xuanshi123)\ **Replies:** 3\ **Last updated:** [December 8, 2023, 4:07am UTC](https://community.freefem.org/t/how-to-implement-normalization-constraint-and-single-value-variable-in-parallel-setting/2824 "2023-12-08T04:07:28Z")
I am doing a lagrange-multipliers problem similar to what is in the page https://doc.freefem.org/examples/finite-element.html#lagrange-multipliers but I am not sure how to set up normalization constrant and the sing… --- ## [The freefem days zoom conference number](https://community.freefem.org/t/the-freefem-days-zoom-conference-number/2821)
**Author:** [@WeiQLiu](https://community.freefem.org/u/WeiQLiu)\ **Replies:** 2\ **Last updated:** [December 7, 2023, 12:57am UTC](https://community.freefem.org/t/the-freefem-days-zoom-conference-number/2821 "2023-12-07T00:57:53Z")
Dear all, I’d like to know the 15th FreeFem++ days Zoom conference number. Did someone share it with me? Thanks a lot! --- ## [Flexible GMRES (fgmres)](https://community.freefem.org/t/flexible-gmres-fgmres/2804)
**Author:** [@Talal](https://community.freefem.org/u/Talal)\ **Replies:** 3\ **Last updated:** [November 26, 2023, 7:43pm UTC](https://community.freefem.org/t/flexible-gmres-fgmres/2804 "2023-11-26T19:43:56Z")
I’m utilizing fGMRES and require guidance on how to implement the restart number. --- ## [Using 3D plots to Make Figures for a Report](https://community.freefem.org/t/using-3d-plots-to-make-figures-for-a-report/2812)
**Author:** [@Archie](https://community.freefem.org/u/Archie)\ **Replies:** 1\ **Last updated:** [November 23, 2023, 7:01pm UTC](https://community.freefem.org/t/using-3d-plots-to-make-figures-for-a-report/2812 "2023-11-23T19:01:13Z")
Is there a way to create a 2D image of a high quality that can be used in a report or a poster from a 3D plot? I have tried ps = “\*\*\*” but regardless of the extension I use, the file created won’t open. Thank you in ad… --- ## [Nonlinear PDE + scalar constraint with PETSc?](https://community.freefem.org/t/nonlinear-pde-scalar-constraint-with-petsc/2810)
**Author:** [@etj](https://community.freefem.org/u/etj)\ **Replies:** 1\ **Last updated:** [November 23, 2023, 12:41pm UTC](https://community.freefem.org/t/nonlinear-pde-scalar-constraint-with-petsc/2810 "2023-11-23T12:41:58Z")
Hello, I would like to solve a nonlinear PDE together with an additional scalar constraint (involving some integral of the PDE solution). I have a working serial code, where I assemble a block matrix and use a “hand-co… --- ## [Interactive graphic command](https://community.freefem.org/t/interactive-graphic-command/2808)
**Author:** [@Christin](https://community.freefem.org/u/Christin)\ **Replies:** 1\ **Last updated:** [November 20, 2023, 8:16am UTC](https://community.freefem.org/t/interactive-graphic-command/2808 "2023-11-20T08:16:37Z")
Hello, Could you please provide an explanation on utilizing the interactive graphical commands + and p in plotting? thanks… --- ## [Brain geometry in 2D or Breast in 2D](https://community.freefem.org/t/brain-geometry-in-2d-or-breast-in-2d/2701)
**Author:** [@lassounon](https://community.freefem.org/u/lassounon)\ **Replies:** 11\ **Last updated:** [November 17, 2023, 2:31pm UTC](https://community.freefem.org/t/brain-geometry-in-2d-or-breast-in-2d/2701 "2023-11-17T14:31:11Z")
Hello community I would like someone to share with me a 2D mesh of the human brain and/or breast. I would like to test some code on these domain types. I haven’t found a solution for this yet, thank you for your help. P… --- ## [Inconsistent Issue with Periodic Condition](https://community.freefem.org/t/inconsistent-issue-with-periodic-condition/2807)
**Author:** [@FluidMan](https://community.freefem.org/u/FluidMan)\ **Replies:** 0\ **Last updated:** [November 16, 2023, 8:40pm UTC](https://community.freefem.org/t/inconsistent-issue-with-periodic-condition/2807 "2023-11-16T20:40:01Z")
Hi all! So I have a 3d mesh that works whenever I use: fespace Vh3(Th3,\[P2,P2,P2,P1\]); but not: fespace Vh3p(Th3, P2, periodic=\[\[Face1, y,z\],\[Face3, y,z\]\]); Crazy enough it does work sometimes if I change the size o… --- ## [Out of memory, catch an erreur in solve =\> set sol = 0!](https://community.freefem.org/t/out-of-memory-catch-an-erreur-in-solve-set-sol-0/2806)
**Author:** [@thingway](https://community.freefem.org/u/thingway)\ **Replies:** 0\ **Last updated:** [November 16, 2023, 12:36pm UTC](https://community.freefem.org/t/out-of-memory-catch-an-erreur-in-solve-set-sol-0/2806 "2023-11-16T12:36:31Z")
Hello, teachers. I’m running the thermally coupled MHD equations and I’m having the following problem. The display is out of memory, when I reduce the mesh size it works but the mesh size is not very large. Please tell m… --- ## [A posteriori adaptmesh](https://community.freefem.org/t/a-posteriori-adaptmesh/2801)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 0\ **Last updated:** [November 15, 2023, 10:58am UTC](https://community.freefem.org/t/a-posteriori-adaptmesh/2801 "2023-11-15T10:58:43Z")
Hello, I saw an example regarding a posteriori error but it’s done in a node. Is there a way to compute the a posteriori in an element K and pass that information to adaptmesh? --- ## [PETSc on 3D Cube with Periodic Boundary Conditions](https://community.freefem.org/t/petsc-on-3d-cube-with-periodic-boundary-conditions/2799)
**Author:** [@GiacomoSperoni97](https://community.freefem.org/u/GiacomoSperoni97)\ **Replies:** 6\ **Last updated:** [November 14, 2023, 2:54pm UTC](https://community.freefem.org/t/petsc-on-3d-cube-with-periodic-boundary-conditions/2799 "2023-11-14T14:54:30Z")
Dear community, I’m interested in using the HPDDM solver by PETSC on a 3D cube with periodic boundary conditions (PBC). Following the 2D example diffusion-periodic-balanced-2d-PETSc.edp, I initially modified it on a ba… --- ## [Solving a BVP with an algebraic equation](https://community.freefem.org/t/solving-a-bvp-with-an-algebraic-equation/2798)
**Author:** [@echarala](https://community.freefem.org/u/echarala)\ **Replies:** 0\ **Last updated:** [November 14, 2023, 1:29am UTC](https://community.freefem.org/t/solving-a-bvp-with-an-algebraic-equation/2798 "2023-11-14T01:29:54Z")
Esteemed FreeFEM community, I have been very much interested in solving BVPs with extra algebraic equations. For your convenience, I am attaching a brief note that describes the system of interest here (it is a simple 1… --- ## [double dot product](https://community.freefem.org/t/double-dot-product/2795)
**Author:** [@m.javad98](https://community.freefem.org/u/m.javad98)\ **Replies:** 0\ **Last updated:** [November 13, 2023, 8:21pm UTC](https://community.freefem.org/t/double-dot-product/2795 "2023-11-13T20:21:45Z")
I have two tensors. How do I compute the double dot product of the two tensors in FreeFEM? --- ## [Sliding boundary in an analysis of an elasticity](https://community.freefem.org/t/sliding-boundary-in-an-analysis-of-an-elasticity/2787)
**Author:** [@Keita](https://community.freefem.org/u/Keita)\ **Replies:** 0\ **Last updated:** [November 10, 2023, 9:10am UTC](https://community.freefem.org/t/sliding-boundary-in-an-analysis-of-an-elasticity/2787 "2023-11-10T09:10:26Z")
Hi FF++ developpers and users. As shown in the figure, I’d like to perform an analysis in which an object is stored by sliding it between upper and lower rails (curves given by y=f(x)) fixed in space. If you know how t… --- ## [FreeFEM days Thursday 7 & Friday 8, December (Zoom link available)](https://community.freefem.org/t/freefem-days-thursday-7-friday-8-december-zoom-link-available/2785)
**Author:** [@prj](https://community.freefem.org/u/prj)\ **Replies:** 0\ **Last updated:** [November 9, 2023, 8:19pm UTC](https://community.freefem.org/t/freefem-days-thursday-7-friday-8-december-zoom-link-available/2785 "2023-11-09T20:19:57Z")
Zoom link: here. --- ## [Finite element space on an edge](https://community.freefem.org/t/finite-element-space-on-an-edge/2774)
**Author:** [@AArnoult](https://community.freefem.org/u/AArnoult)\ **Replies:** 3\ **Last updated:** [November 9, 2023, 11:31am UTC](https://community.freefem.org/t/finite-element-space-on-an-edge/2774 "2023-11-09T11:31:29Z")
Dear FreeFem++ community, For domain decomposition, I need to solve a 2d problem with a given function g on a boundary (thus 1d) obtained with an iterative finite element calculation. g can be, for example, the restrict… --- ## [Order of convergence with no exact solution given](https://community.freefem.org/t/order-of-convergence-with-no-exact-solution-given/2750)
**Author:** [@AbuAzzan](https://community.freefem.org/u/AbuAzzan)\ **Replies:** 5\ **Last updated:** [November 9, 2023, 7:37am UTC](https://community.freefem.org/t/order-of-convergence-with-no-exact-solution-given/2750 "2023-11-09T07:37:08Z")
Hi all Freefem developers and users I am concerned with calculating the order of convergence when no exact solution of an elliptic PDE is given. One way to determine its value at a grid point x is by ϑ\_{i}=((log|u(x;{h{… --- ## [Select the same node on adjacent faces](https://community.freefem.org/t/select-the-same-node-on-adjacent-faces/2783)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 0\ **Last updated:** [November 7, 2023, 2:07pm UTC](https://community.freefem.org/t/select-the-same-node-on-adjacent-faces/2783 "2023-11-07T14:07:56Z")
Dear all, Given a mesh 3D, I need to select one node in each face. Given 2 adjacent faces, how to be sure that we select the same node on these two faces ? I put in attachment my test case. You will find the way I sele… --- ## [A question about calculation of the energy based on finite elements](https://community.freefem.org/t/a-question-about-calculation-of-the-energy-based-on-finite-elements/2759)
**Author:** [@m31phy](https://community.freefem.org/u/m31phy)\ **Replies:** 1\ **Last updated:** [November 6, 2023, 7:01pm UTC](https://community.freefem.org/t/a-question-about-calculation-of-the-energy-based-on-finite-elements/2759 "2023-11-06T19:01:57Z")
Dear all. I have a quick question about calculating the energy or other functions in FreeFEM++. I already obtained proper solutions (e.g., finite elements in space) using FreeFEM++. For instance, let’s assume that we c… --- ## [Problem swap: the point s is on an edge](https://community.freefem.org/t/problem-swap-the-point-s-is-on-an-edge/2772)
**Author:** [@jna1g18](https://community.freefem.org/u/jna1g18)\ **Replies:** 1\ **Last updated:** [November 3, 2023, 8:09am UTC](https://community.freefem.org/t/problem-swap-the-point-s-is-on-an-edge/2772 "2023-11-03T08:09:43Z")
Hi all, I received the following message while running my code: “Problem swap: the point s is on an edge =\> swap 0 \[480689017::1911157094,1911153325,1911153324,{480688784 4} {480696710 0} {480696711 0} \]” Can anyone te… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=24) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=26)