# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=46 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 47 --- ## [Execution macro error \* \<10LinearCombI7MGauche4C\_F0E\>](https://community.freefem.org/t/execution-macro-error-10linearcombi7mgauche4c-f0e/1744)
**Author:** [@bomber](https://community.freefem.org/u/bomber)\ **Replies:** 2\ **Last updated:** [May 22, 2022, 1:53pm UTC](https://community.freefem.org/t/execution-macro-error-10linearcombi7mgauche4c-f0e/1744 "2022-05-22T13:53:18Z")
Hello, I’m a new Freefem user; I’d like to solve the following equation ∂∆φ/∂t+∂φ/∂x ∂∆φ/∂y-∂φ/∂y ∂∆φ/∂x=0 begin φ a scalar potential; I implemented the weak formulation of the problem using the freeFEM syntax, u… --- ## [Load error: MUMPS\_FreeFem](https://community.freefem.org/t/load-error-mumps-freefem/1762)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 1\ **Last updated:** [May 21, 2022, 4:00pm UTC](https://community.freefem.org/t/load-error-mumps-freefem/1762 "2022-05-21T16:00:00Z")
I used the example in the reference book. Why can’t it run? load “MUMPS\_FreeFem” //default solver: real-\> MUMPS, complex → MUMPS load “real\_SuperLU\_DIST\_FreeFem” default solver: real-\> SuperLU\_DIST, complex → MUMPS … --- ## [The command "cout" does not output the result](https://community.freefem.org/t/the-command-cout-does-not-output-the-result/1759)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 1\ **Last updated:** [May 20, 2022, 1:46pm UTC](https://community.freefem.org/t/the-command-cout-does-not-output-the-result/1759 "2022-05-20T13:46:56Z")
Use this command C:\\Users\\DELL\>FreeFem+±mpi 05.15学习程序书.edp to run the following program, load “MPICG” load “medit” load “metis” include “getARGV.idp” include “MPIplot.idp” include “MPIGMRESmacro.idp” searchMe… --- ## [Number of processes and memory usage](https://community.freefem.org/t/number-of-processes-and-memory-usage/1551)
**Author:** [@aszaboa](https://community.freefem.org/u/aszaboa)\ **Replies:** 15\ **Last updated:** [May 20, 2022, 1:16pm UTC](https://community.freefem.org/t/number-of-processes-and-memory-usage/1551 "2022-05-20T13:16:33Z")
Dear FreeFem users, when I run FreeFem in parallel on e.g., 5 processes, it also starts 10 sleeping processes. These processes seem to consume memory. Should I be worried about this? That is the reason for this? See als… --- ## [These symbols mean?](https://community.freefem.org/t/these-symbols-mean/1761)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 2\ **Last updated:** [May 20, 2022, 12:48pm UTC](https://community.freefem.org/t/these-symbols-mean/1761 "2022-05-20T12:48:52Z")
What do these symbols mean? u \*= 1./N; b += bc1; b2 += bc2; --- ## [The value on the grid node](https://community.freefem.org/t/the-value-on-the-grid-node/1757)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [May 19, 2022, 6:32am UTC](https://community.freefem.org/t/the-value-on-the-grid-node/1757 "2022-05-19T06:32:43Z")
In the process of time iteration, the finite element solution obtained at each step is actually the value on the grid node, but (3,0.5) is not the grid node. Why can it be obtained? mesh Th = square(30, 5, \[6.\*x,y\]); … --- ## [Double Dot Product or Inner Product of Two Tensors](https://community.freefem.org/t/double-dot-product-or-inner-product-of-two-tensors/1756)
**Author:** [@D\_N\_Sarkar](https://community.freefem.org/u/D_N_Sarkar)\ **Replies:** 0\ **Last updated:** [May 19, 2022, 4:23am UTC](https://community.freefem.org/t/double-dot-product-or-inner-product-of-two-tensors/1756 "2022-05-19T04:23:03Z")
I have two tensors. How do I compute the double dot product or inner product of the two tensors in FreeFEM? --- ## [Fflapack failed](https://community.freefem.org/t/fflapack-failed/1752)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 3\ **Last updated:** [May 19, 2022, 2:29am UTC](https://community.freefem.org/t/fflapack-failed/1752 "2022-05-19T02:29:45Z")
load “fflapack” Load error: fflapack fail: list prefix: 'E:\\FreeFem++\\.' list suffix: ‘’ , ‘.dll’ current line = 210 Load error : fflapack line number :210, fflapack error Load error : fflapack line number :210,… --- ## [Weird behaviour of 3D Periodic spaces](https://community.freefem.org/t/weird-behaviour-of-3d-periodic-spaces/1753)
**Author:** [@salah](https://community.freefem.org/u/salah)\ **Replies:** 3\ **Last updated:** [May 18, 2022, 5:22pm UTC](https://community.freefem.org/t/weird-behaviour-of-3d-periodic-spaces/1753 "2022-05-18T17:22:42Z")
Hello everyone, While experimenting with periodic elements on a cubic mesh with an inclusion, I tried to write down a basic loop to display the values of my solution at the interface. The code gives back an array length… --- ## [Midpoint method giving flickering result](https://community.freefem.org/t/midpoint-method-giving-flickering-result/1743)
**Author:** [@fas41](https://community.freefem.org/u/fas41)\ **Replies:** 2\ **Last updated:** [May 18, 2022, 1:49pm UTC](https://community.freefem.org/t/midpoint-method-giving-flickering-result/1743 "2022-05-18T13:49:27Z")
I have shared the code here and screenshot of the pde:Please ignore the error calculating part in the code since I am not doing it for known exact solution: // A step of the midpoint method can be carried out by firs… --- ## [FreeFem++-mpi .exe failed to run example mpi.edp](https://community.freefem.org/t/freefem-mpi-exe-failed-to-run-example-mpi-edp/1548)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 1\ **Last updated:** [May 18, 2022, 4:38am UTC](https://community.freefem.org/t/freefem-mpi-exe-failed-to-run-example-mpi-edp/1548 "2022-05-18T04:38:36Z")
Hello everyone, MSMPI has been successfully debugged, with cmd （C:\>“Program Files\\Microsoft MPI\\Bin\\mpiexec.exe”） can be successfully started, FreeFem+±mpi .exe （C:\>“Program Files (x86)\\FreeFem++\\FreeFem+±mpi.exe”） … --- ## [Changing a parameter within border command](https://community.freefem.org/t/changing-a-parameter-within-border-command/1749)
**Author:** [@amtravco](https://community.freefem.org/u/amtravco)\ **Replies:** 2\ **Last updated:** [May 17, 2022, 1:05pm UTC](https://community.freefem.org/t/changing-a-parameter-within-border-command/1749 "2022-05-17T13:05:49Z")
Suppose I create a border using real a = 1; border b1(t=0,1){x=a\*t;y=t;} Then I create a second border using the identical code, but with variable a changed: a = 2; border b2(t=0,1){x=a\*t;y=t;} These two borders are … --- ## [Streamfunction of a vector field](https://community.freefem.org/t/streamfunction-of-a-vector-field/1740)
**Author:** [@Helene](https://community.freefem.org/u/Helene)\ **Replies:** 5\ **Last updated:** [May 17, 2022, 1:01pm UTC](https://community.freefem.org/t/streamfunction-of-a-vector-field/1740 "2022-05-17T13:01:31Z")
Hello, I just discovered Freefem and use it for my master degree in bioscience. I’d like to visualize the streamlines of a 2d vector field so that their isolines must be always orthogonal to the vector field. The “stre… --- ## [Why ?Try to get unset x,y,](https://community.freefem.org/t/why-try-to-get-unset-x-y/1735)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 1\ **Last updated:** [May 16, 2022, 12:00pm UTC](https://community.freefem.org/t/why-try-to-get-unset-x-y/1735 "2022-05-16T12:00:25Z")
Good morning. The code can run in 2D, but it can’t run in 3D. I found that the original line of code can’t run in 3D. The code is as follows if(psai0\>=1-k) { Eq1; } psai0=psai1; --- ## [Forced equality between two fields](https://community.freefem.org/t/forced-equality-between-two-fields/1739)
**Author:** [@mchetoui](https://community.freefem.org/u/mchetoui)\ **Replies:** 1\ **Last updated:** [May 16, 2022, 11:52am UTC](https://community.freefem.org/t/forced-equality-between-two-fields/1739 "2022-05-16T11:52:46Z")
Hello every one, I have a problem with 6 unknown fields (ux1,uy1,ux2,uy2,p1,p2) and 6 test functions (vx1,vy1,vx2,vy2,q1,q2). My geometry is a square (0,1)(0,1) divided in two equal rectangle by a vertical internal line… --- ## [Can freefem + + find the largest element of the stiffness matrix?](https://community.freefem.org/t/can-freefem-find-the-largest-element-of-the-stiffness-matrix/1736)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 6\ **Last updated:** [May 16, 2022, 6:51am UTC](https://community.freefem.org/t/can-freefem-find-the-largest-element-of-the-stiffness-matrix/1736 "2022-05-16T06:51:46Z")
Can freefem + + find the largest element of the stiffness matrix? --- ## [Plugin with 13 parameters](https://community.freefem.org/t/plugin-with-13-parameters/1732)
**Author:** [@e-aranda](https://community.freefem.org/u/e-aranda)\ **Replies:** 5\ **Last updated:** [May 12, 2022, 3:33pm UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732 "2022-05-12T15:33:36Z")
Hello, I am trying to build some C++ function to link with FreeFem++. Something like: (dummy example) “”" #include using namespace std; #include “error.hpp” #include “AFunction.hpp” #include “AFunction\_ext.hpp” … --- ## [Convect function failing](https://community.freefem.org/t/convect-function-failing/1726)
**Author:** [@simbar](https://community.freefem.org/u/simbar)\ **Replies:** 2\ **Last updated:** [May 12, 2022, 10:14am UTC](https://community.freefem.org/t/convect-function-failing/1726 "2022-05-12T10:14:48Z")
Hi everyone, I am currently using FreeFEM to model the kuramoto sivashinsky equation u\_{t}+\\nu u\_{xxxx}+u\_{xx}+uu\_{x}=0 with periuodic spatial and temporal boundary conditions. I am modeling this equation by differe… --- ## [How to export a rhs into petsc](https://community.freefem.org/t/how-to-export-a-rhs-into-petsc/1730)
**Author:** [@DuanXY](https://community.freefem.org/u/DuanXY)\ **Replies:** 5\ **Last updated:** [May 12, 2022, 2:49pm UTC](https://community.freefem.org/t/how-to-export-a-rhs-into-petsc/1730 "2022-05-12T14:49:45Z")
Hi, In my work, it’s more convenient to export matrix and RHS to PETSc to solve Ax=b. Because I want to develop a special efficient solving method for the problem based on PETSc. I want to export a PETSc VECMPI type fr… --- ## [Solve coupled PDE](https://community.freefem.org/t/solve-coupled-pde/1728)
**Author:** [@MAS-OUD](https://community.freefem.org/u/MAS-OUD)\ **Replies:** 1\ **Last updated:** [May 11, 2022, 7:28am UTC](https://community.freefem.org/t/solve-coupled-pde/1728 "2022-05-11T07:28:28Z")
Hello. How can I input the following problem in FREEFEM? It is actually a coupled PDE, and the coefficients in the weak form are matrices instead of scalars. Thanks in advance --- ## [Two imported mesh domains](https://community.freefem.org/t/two-imported-mesh-domains/1706)
**Author:** [@mchetoui](https://community.freefem.org/u/mchetoui)\ **Replies:** 4\ **Last updated:** [May 5, 2022, 8:00am UTC](https://community.freefem.org/t/two-imported-mesh-domains/1706 "2022-05-05T08:00:08Z")
Hello everyone, I try to solve two different PDEs in two 3D domains separated by a shared interface. The two problems are coupled through this interface. The two domains are realistic so I need to import them as .msh. I… --- ## [Addressing edges of a boundary](https://community.freefem.org/t/addressing-edges-of-a-boundary/1714)
**Author:** [@mahdi](https://community.freefem.org/u/mahdi)\ **Replies:** 1\ **Last updated:** [May 5, 2022, 2:47am UTC](https://community.freefem.org/t/addressing-edges-of-a-boundary/1714 "2022-05-05T02:47:43Z")
Hi I want to address the edges of an internal border (for instance, label=1). Does the label on a border refer to the elements or edges? To explain better, “NtonEdge” is a boolean that discusses the edges and can be us… --- ## [Using FreeFEM to model Kuramoto Sivashinsky Equation](https://community.freefem.org/t/using-freefem-to-model-kuramoto-sivashinsky-equation/1717)
**Author:** [@simbar](https://community.freefem.org/u/simbar)\ **Replies:** 0\ **Last updated:** [May 4, 2022, 5:25pm UTC](https://community.freefem.org/t/using-freefem-to-model-kuramoto-sivashinsky-equation/1717 "2022-05-04T17:25:37Z")
Hi everyone I am attempting to model the Kuramoto Sivashinsky equation using FreeFEM. The equation has the form: u\_{t}+\\nu u\_{xxxx}+u\_{xx}+uu\_{x}=0 \\noindent With 1-periodic boundary condition u(\\cdot,0) = u\_{0… --- ## [How to apply point forces to a mesh?](https://community.freefem.org/t/how-to-apply-point-forces-to-a-mesh/1715)
**Author:** [@rubendev](https://community.freefem.org/u/rubendev)\ **Replies:** 2\ **Last updated:** [May 4, 2022, 1:57pm UTC](https://community.freefem.org/t/how-to-apply-point-forces-to-a-mesh/1715 "2022-05-04T13:57:23Z")
Hello, I am trying to apply a point force on my mesh but I have been unsuccessful so far. I have modified the code from the FreeFem Modules (3d elasticity case) to fit my application, except I can’t seem to be able to a… --- ## [Im new to FreeFem, can someone clear up what my program is actually doing?](https://community.freefem.org/t/im-new-to-freefem-can-someone-clear-up-what-my-program-is-actually-doing/1713)
**Author:** [@rubendev](https://community.freefem.org/u/rubendev)\ **Replies:** 2\ **Last updated:** [May 4, 2022, 11:13am UTC](https://community.freefem.org/t/im-new-to-freefem-can-someone-clear-up-what-my-program-is-actually-doing/1713 "2022-05-04T11:13:47Z")
Basically as the title says Im learning FreeFem for a university project and I want to better understand what the program is actually doing. I have the following program modified from https://modules.freefem.org/modules/… --- ## [Lines missing in 3D algorithm of magnetostatic module](https://community.freefem.org/t/lines-missing-in-3d-algorithm-of-magnetostatic-module/1696)
**Author:** [@FEMfisH](https://community.freefem.org/u/FEMfisH)\ **Replies:** 7\ **Last updated:** [May 3, 2022, 5:24pm UTC](https://community.freefem.org/t/lines-missing-in-3d-algorithm-of-magnetostatic-module/1696 "2022-05-03T17:24:43Z")
Hi, it seems that there are missing some lines at the end of the 3D algorithm of the magnetostatic module. At least a plot command should be there. Does anybody know, what is missing? --- ## [Building a function in which one of its inputs is a variable of type Vh](https://community.freefem.org/t/building-a-function-in-which-one-of-its-inputs-is-a-variable-of-type-vh/1712)
**Author:** [@lucassfernandez](https://community.freefem.org/u/lucassfernandez)\ **Replies:** 4\ **Last updated:** [May 3, 2022, 1:52pm UTC](https://community.freefem.org/t/building-a-function-in-which-one-of-its-inputs-is-a-variable-of-type-vh/1712 "2022-05-03T13:52:45Z")
Hi, folks! Suppose I have: int n; real\[int\] vi; mesh Th; fespace Vh(Th, P1); Vh u; I’d like to build a function in which one of its inputs is u, i.e., the variable of Vh-type. For example: func int myfunction(int n, … --- ## [Manually assign nodal/elemental values](https://community.freefem.org/t/manually-assign-nodal-elemental-values/1709)
**Author:** [@manasnk](https://community.freefem.org/u/manasnk)\ **Replies:** 0\ **Last updated:** [May 2, 2022, 6:11am UTC](https://community.freefem.org/t/manually-assign-nodal-elemental-values/1709 "2022-05-02T06:11:57Z")
I am totally new to FreeFEM and I want to change some lines from a specific code. I need some help. Thank you in advance. CASE-1 real L = 4; real W = 1; real v = 0.5; border b1(t = -0.025W, 0.025W){x = 0.5L; y = t;… --- ## [Mesh generation when the number of border portions changes](https://community.freefem.org/t/mesh-generation-when-the-number-of-border-portions-changes/1703)
**Author:** [@lucassfernandez](https://community.freefem.org/u/lucassfernandez)\ **Replies:** 2\ **Last updated:** [May 1, 2022, 7:32pm UTC](https://community.freefem.org/t/mesh-generation-when-the-number-of-border-portions-changes/1703 "2022-05-01T19:32:46Z")
Hi, folks! I’m dealing with a very interesting problem in 2D where the geometric domain is given by the union of unit balls. As the center of each unit ball is relocated based on an optimization process, the geometric d… --- ## [Finite element nodes](https://community.freefem.org/t/finite-element-nodes/1701)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 3\ **Last updated:** [May 1, 2022, 1:43pm UTC](https://community.freefem.org/t/finite-element-nodes/1701 "2022-05-01T13:43:18Z")
Hello, can freefem + + store finite element nodes instead of mesh nodes? [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=45) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=47)