# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=54 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 55 --- ## [Test function do not exist](https://community.freefem.org/t/test-function-do-not-exist/1315)
**Author:** [@xiaojiemo](https://community.freefem.org/u/xiaojiemo)\ **Replies:** 1\ **Last updated:** [November 9, 2021, 3:12am UTC](https://community.freefem.org/t/test-function-do-not-exist/1315 "2021-11-09T03:12:14Z")
hello,everyone, I meet a peoblem. I am solving a coupled equation.when I put two variables, everything works well. while, after I put the third one, the procedure told me that the test funtion of this variable do not ex… --- ## [Qforder (qfV=qfV1lump)](https://community.freefem.org/t/qforder-qfv-qfv1lump/744)
**Author:** [@Mik](https://community.freefem.org/u/Mik)\ **Replies:** 1\ **Last updated:** [November 7, 2021, 9:19am UTC](https://community.freefem.org/t/qforder-qfv-qfv1lump/744 "2021-11-07T09:19:44Z")
Dear All, I have a question regarding the qforder, more specifically on qfV=qfV1lump. When I implement qfV=qfV1lump instead of default value, my program (P1 space) runs almost 3 to 5 times faster, with improved accurac… --- ## [Scope the scope - unexpected function behaviour](https://community.freefem.org/t/scope-the-scope-unexpected-function-behaviour/1298)
**Author:** [@aszaboa](https://community.freefem.org/u/aszaboa)\ **Replies:** 1\ **Last updated:** [November 6, 2021, 7:40pm UTC](https://community.freefem.org/t/scope-the-scope-unexpected-function-behaviour/1298 "2021-11-06T19:40:00Z")
Just out of curiosity, does anyone know that in the following script: func real fun1(complex in1){ cout \<\< "in fun1: in1=" \<\< in1 \<\< endl; complex in12Scope = in1; func real fun2(complex in2){ … --- ## [Unexpected output when summing two fespace variables](https://community.freefem.org/t/unexpected-output-when-summing-two-fespace-variables/1309)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [November 6, 2021, 5:01pm UTC](https://community.freefem.org/t/unexpected-output-when-summing-two-fespace-variables/1309 "2021-11-06T17:01:00Z")
Here is my sample code real x0 = 0, x1 = 1.; real y0 = 0, y1 = 0.5; int n = 2, m = 1; mesh Th = square(n, m, \[x0 + (x1 - x0) \* x, y0 + (y1 - y0) \* y\]); mesh uTh = Th; macro res \[rx, ry\] // EOM // Residuum. macro resEl … --- ## [Issues regarding msh3 and the Sphere function](https://community.freefem.org/t/issues-regarding-msh3-and-the-sphere-function/1307)
**Author:** [@Gronaz](https://community.freefem.org/u/Gronaz)\ **Replies:** 0\ **Last updated:** [November 5, 2021, 5:34pm UTC](https://community.freefem.org/t/issues-regarding-msh3-and-the-sphere-function/1307 "2021-11-05T17:34:35Z")
Hello, I am trying to create surface meshes, and more specifically, I am trying to use the Sphere function. Unfortunately, I get the error message : The Identifier Sphere does not exist. I am very new to FreeFem++ and … --- ## [Computing strains and stresses: per mesh vertice or element?](https://community.freefem.org/t/computing-strains-and-stresses-per-mesh-vertice-or-element/1286)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [November 4, 2021, 6:37pm UTC](https://community.freefem.org/t/computing-strains-and-stresses-per-mesh-vertice-or-element/1286 "2021-11-04T18:37:54Z")
Hi, So I am not sure how FreeFem++ works, but I know that Abaqus for example has: Displacements computed in the vertices While strains and stresses are computed per finite element in Gaussian points. However, I am no… --- ## [Function to fill fespace](https://community.freefem.org/t/function-to-fill-fespace/1297)
**Author:** [@ivan](https://community.freefem.org/u/ivan)\ **Replies:** 2\ **Last updated:** [November 4, 2021, 6:17pm UTC](https://community.freefem.org/t/function-to-fill-fespace/1297 "2021-11-04T18:17:48Z")
Hello all, I would like to know what are the available methods to assign values to a fespace variable. I am trying to solve a transient diffusion problem where the diffusivity depends upon the variable of interest. Fo… --- ## [Function mean unexpected behaviour](https://community.freefem.org/t/function-mean-unexpected-behaviour/1296)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 4\ **Last updated:** [November 4, 2021, 5:50pm UTC](https://community.freefem.org/t/function-mean-unexpected-behaviour/1296 "2021-11-04T17:50:44Z")
Could somebody please explain the behaviour of mean function? For example this case works: real x0 = 0, x1 = 1.; real y0 = 0, y1 = 0.5; int n = 80, m = 40; mesh Th = square(n, m, \[x0 + (x1 - x0) \* x, y0 + (y1 - y0) \* y… --- ## [Fenics vs FreeFem](https://community.freefem.org/t/fenics-vs-freefem/1300)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 0\ **Last updated:** [November 4, 2021, 4:56pm UTC](https://community.freefem.org/t/fenics-vs-freefem/1300 "2021-11-04T16:56:36Z")
Hi, I am trying to rewrite the Fenics example to FreeFem++ and I ran into some problems when I tried to rewrite the following piece metadata = {"quadrature\_degree": deg\_stress, "quadrature\_scheme": "default"} dxm = dx(… --- ## [How to mesh annulus?](https://community.freefem.org/t/how-to-mesh-annulus/1295)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [November 3, 2021, 9:49pm UTC](https://community.freefem.org/t/how-to-mesh-annulus/1295 "2021-11-03T21:49:11Z")
Hi, I tried to mesh annulus with different number of nodes on the inner radius: real r1 = 1.0; real r2 = 1.3; border outter(t = 0, pi / 2.){x = r2 \* cos(t); y = r2 \* sin(t); label=1;} border inner(t = 0, pi / 2.){x = r… --- ## [Obtaining the strain-displacement matrix](https://community.freefem.org/t/obtaining-the-strain-displacement-matrix/1291)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 4\ **Last updated:** [November 2, 2021, 2:25pm UTC](https://community.freefem.org/t/obtaining-the-strain-displacement-matrix/1291 "2021-11-02T14:25:08Z")
In FEM, the displacements are known in mesh nodes. The strain tensor Eps is then computed using the strain-displacement matrix, usually noted with B, so that Eps= B u for displacement vector u. Additionally, stress tens… --- ## [Real world example?](https://community.freefem.org/t/real-world-example/1283)
**Author:** [@Bul](https://community.freefem.org/u/Bul)\ **Replies:** 4\ **Last updated:** [October 30, 2021, 8:08am UTC](https://community.freefem.org/t/real-world-example/1283 "2021-10-30T08:08:35Z")
Are there any accessible (both physically and intellectually) examples of modelling a recognisibly real world problem\*? Any type would be good, but specifically a magneto-dynamic would be most useful. \*By which I mean,… --- ## [Save results to restart a piece of code](https://community.freefem.org/t/save-results-to-restart-a-piece-of-code/1292)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 1\ **Last updated:** [October 30, 2021, 1:10am UTC](https://community.freefem.org/t/save-results-to-restart-a-piece-of-code/1292 "2021-10-30T01:10:22Z")
What is the right command to write and read a fem variable? It seems there are many about write and read meshes, but I did not find the command to save and read a fem variable u; fespace Vh(Th, P1); Vh u; --- ## [Boundary condition in Newton method](https://community.freefem.org/t/boundary-condition-in-newton-method/1284)
**Author:** [@tess35](https://community.freefem.org/u/tess35)\ **Replies:** 3\ **Last updated:** [October 29, 2021, 4:28pm UTC](https://community.freefem.org/t/boundary-condition-in-newton-method/1284 "2021-10-29T16:28:42Z")
Hi everybody, I search how to put the boundary condition in the Newton method , for Dirichlet , Neumann or Robin condition. For example, solving the toy equation d2 u(x) /dx2 + u(x) -1 =0, u(0)=1, u(1)=10. It’… --- ## [Mpiallreduce probelm](https://community.freefem.org/t/mpiallreduce-probelm/1290)
**Author:** [@zcwang6](https://community.freefem.org/u/zcwang6)\ **Replies:** 2\ **Last updated:** [October 28, 2021, 4:01pm UTC](https://community.freefem.org/t/mpiallreduce-probelm/1290 "2021-10-28T16:01:43Z")
Hello there, a quick question about MPIALLREDUCE; I used this function in the following script mpiComm Comm(mpiCommWorld, 0, 0); real nubl = mpirank; real nubg=0; mpiAllReduce(nubg, nubl, mpiCommWorld, mpiSUM); cout… --- ## [Convect( ) in parallel](https://community.freefem.org/t/convect-in-parallel/1270)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 5\ **Last updated:** [October 28, 2021, 12:46pm UTC](https://community.freefem.org/t/convect-in-parallel/1270 "2021-10-28T12:46:59Z")
Just to confirm that convect( ) has already been implemented in parallel? For example, if \[ux,uy\] is convected from one partition of mesh to another, has this been considered already in the parallel implementation so th… --- ## [Poor residuals from PETSc iterative solver for 3D elasticity equation](https://community.freefem.org/t/poor-residuals-from-petsc-iterative-solver-for-3d-elasticity-equation/1288)
**Author:** [@KBarrett](https://community.freefem.org/u/KBarrett)\ **Replies:** 3\ **Last updated:** [October 28, 2021, 6:50am UTC](https://community.freefem.org/t/poor-residuals-from-petsc-iterative-solver-for-3d-elasticity-equation/1288 "2021-10-28T06:50:45Z")
Hello all, I am experiencing poor residuals with my iterative solver in PETSc when solving the elasticity equation. I normally use -pc\_gamg and -ksp\_gmres, and I have not had issues with solving 3D meshes when my Young’… --- ## [Sorry in optimization element\_OP plein 3d](https://community.freefem.org/t/sorry-in-optimization-element-op-plein-3d/1287)
**Author:** [@xiaojiemo](https://community.freefem.org/u/xiaojiemo)\ **Replies:** 0\ **Last updated:** [October 27, 2021, 8:03am UTC](https://community.freefem.org/t/sorry-in-optimization-element-op-plein-3d/1287 "2021-10-27T08:03:46Z")
dear all, I am solving two equation using newton method and meets problem in title. My whole procedure is below: solve fi(\[setaf,fi\],\[dsetaf,dfi\],solver=“UMFPACK64”)= 96 : int3d(th2)(cnewtondset… --- ## [Data Export for 3D Cube?](https://community.freefem.org/t/data-export-for-3d-cube/1275)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 1\ **Last updated:** [October 27, 2021, 7:21am UTC](https://community.freefem.org/t/data-export-for-3d-cube/1275 "2021-10-27T07:21:23Z")
I am trying to print the result at a specified point in a 3D cubic domain by the script: cout\<\< "value of T at (0,0,0) = "\<\< T(0,0,0)\<\ **Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 1\ **Last updated:** [October 26, 2021, 2:32pm UTC](https://community.freefem.org/t/mesh-connectivity-details/1285 "2021-10-26T14:32:41Z") I want to be able to: Give point coordinates and as a result get the finite element (or at least its index). Give mesh vertice and as result get list of element indexes, containing this vertice Give the final element i… --- ## [FreeFEM days Thursday 9 & Friday 10, December (hybrid conference)](https://community.freefem.org/t/freefem-days-thursday-9-friday-10-december-hybrid-conference/1196)
**Author:** [@prj](https://community.freefem.org/u/prj)\ **Replies:** 2\ **Last updated:** [October 25, 2021, 1:15pm UTC](https://community.freefem.org/t/freefem-days-thursday-9-friday-10-december-hybrid-conference/1196 "2021-10-25T13:15:20Z")
Registration link: FreeFEM Days - 13th Edition. Update: conference information (Zoom and schedule). --- ## [Stress divergence after elastic deformation does not equal 0, but it should](https://community.freefem.org/t/stress-divergence-after-elastic-deformation-does-not-equal-0-but-it-should/1282)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 0\ **Last updated:** [October 25, 2021, 9:41am UTC](https://community.freefem.org/t/stress-divergence-after-elastic-deformation-does-not-equal-0-but-it-should/1282 "2021-10-25T09:41:05Z")
TL;DR According to the analytical solution (link) for a deflection of a cantilever beam, the divergence of the stress field should equal 0, but my FEM simulations do not result in zero. Problem A simple two-dimensional … --- ## [The 2d field data(eigenvector) without orientation information in Paraview](https://community.freefem.org/t/the-2d-field-data-eigenvector-without-orientation-information-in-paraview/1281)
**Author:** [@wby](https://community.freefem.org/u/wby)\ **Replies:** 0\ **Last updated:** [October 25, 2021, 5:55am UTC](https://community.freefem.org/t/the-2d-field-data-eigenvector-without-orientation-information-in-paraview/1281 "2021-10-25T05:55:11Z")
Hi~ Recently, I found that the eigenvector saved in FreeFem/share/FreeFEM/4.9/examples/eigen/BeamEigenValue.edp When I save the data to the \*.vtu, and there is without orientation information in ParaView. And the cod… --- ## [Initializing a matrix\ with matrix](https://community.freefem.org/t/initializing-a-matrix-complex-with-matrix/1279)
**Author:** [@LorenzoAudibert](https://community.freefem.org/u/LorenzoAudibert)\ **Replies:** 1\ **Last updated:** [October 24, 2021, 3:31pm UTC](https://community.freefem.org/t/initializing-a-matrix-complex-with-matrix/1279 "2021-10-24T15:31:46Z")
Hello eveyone, I could not find the proper way to put a matrix into a matrix complex. Thank you for your help, Lorenzo --- ## [Max() in parallel](https://community.freefem.org/t/max-in-parallel/1278)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 1\ **Last updated:** [October 24, 2021, 2:40pm UTC](https://community.freefem.org/t/max-in-parallel/1278 "2021-10-24T14:40:20Z")
Is there an easy method to compute the maximum of u\[\] in parallel code? fespace Vh(Th, P2); Vh u; --- ## [Is it possible to use cwipi with FreeFem++ to couple it with another code?](https://community.freefem.org/t/is-it-possible-to-use-cwipi-with-freefem-to-couple-it-with-another-code/1274)
**Author:** [@Markov](https://community.freefem.org/u/Markov)\ **Replies:** 0\ **Last updated:** [October 22, 2021, 7:06pm UTC](https://community.freefem.org/t/is-it-possible-to-use-cwipi-with-freefem-to-couple-it-with-another-code/1274 "2021-10-22T19:06:08Z")
I want to know if it possible to couple FreeFem++ with another code using cwipi. --- ## [Umfpack64 can not work](https://community.freefem.org/t/umfpack64-can-not-work/1263)
**Author:** [@xiaojiemo](https://community.freefem.org/u/xiaojiemo)\ **Replies:** 2\ **Last updated:** [October 22, 2021, 10:51am UTC](https://community.freefem.org/t/umfpack64-can-not-work/1263 "2021-10-22T10:51:32Z")
after loading, while it can not work. and the character “defaulttoUMFPACK64()” can not be identified. --- ## [Run FreeFEM with single precision](https://community.freefem.org/t/run-freefem-with-single-precision/1269)
**Author:** [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)\ **Replies:** 2\ **Last updated:** [October 21, 2021, 8:05am UTC](https://community.freefem.org/t/run-freefem-with-single-precision/1269 "2021-10-21T08:05:26Z")
Hello, In the changelog of version 4.6 it is written that FreeFem can solve problems with single precision or 64 bit integers. How can a FreeFem script be run with single precision? I would like to use this feature to … --- ## [Location of computational points](https://community.freefem.org/t/location-of-computational-points/1271)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [October 22, 2021, 7:18am UTC](https://community.freefem.org/t/location-of-computational-points/1271 "2021-10-22T07:18:03Z")
Hi, Is it possible to get the locations of the computational points? For example if a mesh has Th.nv = 1000 points and I am using P2 elements, there are more computational points than mesh vertices. But is there a way … --- ## [Perfectly Matched Layers](https://community.freefem.org/t/perfectly-matched-layers/1266)
**Author:** [@mrziema2](https://community.freefem.org/u/mrziema2)\ **Replies:** 0\ **Last updated:** [October 19, 2021, 1:45pm UTC](https://community.freefem.org/t/perfectly-matched-layers/1266 "2021-10-19T13:45:10Z")
Hi everyone! I’m new to FreeFEM, but am liking it a lot so far. I’m implementing a simple electrostatic problem similar to the wifi propagation example problem (Wifi Propagation). In my implementation, I want an infin… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=53) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=55)