# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=48 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 49 --- ## [Linear problem depending on a nonlinear solution and an eigenmode, in parallel](https://community.freefem.org/t/linear-problem-depending-on-a-nonlinear-solution-and-an-eigenmode-in-parallel/1638)
**Author:** [@etj](https://community.freefem.org/u/etj)\ **Replies:** 6\ **Last updated:** [April 4, 2022, 8:56pm UTC](https://community.freefem.org/t/linear-problem-depending-on-a-nonlinear-solution-and-an-eigenmode-in-parallel/1638 "2022-04-04T20:56:14Z")
Hello, I am using two codes, in parallel: one to solve with PETSc (SNESSolve) a nonlinear problem → let’s call the solution u, one to solve with SLEPc complex (EPSSolve) an eigenvalue problem that depends on u → let’… --- ## [Print the solution at points](https://community.freefem.org/t/print-the-solution-at-points/1643)
**Author:** [@omar](https://community.freefem.org/u/omar)\ **Replies:** 3\ **Last updated:** [April 4, 2022, 4:14pm UTC](https://community.freefem.org/t/print-the-solution-at-points/1643 "2022-04-04T16:14:14Z")
Dear all, I am new to FreeFEM. I am solving Poisson’s equation. and I want to print the u solution to a text file. The solution printed include the solution at nodes and at cells as well. How can I print the solutio… --- ## [Initial guess for iterative solver](https://community.freefem.org/t/initial-guess-for-iterative-solver/1641)
**Author:** [@Amin](https://community.freefem.org/u/Amin)\ **Replies:** 2\ **Last updated:** [April 3, 2022, 4:58pm UTC](https://community.freefem.org/t/initial-guess-for-iterative-solver/1641 "2022-04-03T16:58:28Z")
Hello everyone, How can I use the initial value for x to solve the system of linear equations Ax = b? set(A, solver=GMRES); x\[\] = A^-1\*b\[\]; --- ## [Dirichlet boundary condition](https://community.freefem.org/t/dirichlet-boundary-condition/1639)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [April 2, 2022, 11:33am UTC](https://community.freefem.org/t/dirichlet-boundary-condition/1639 "2022-04-02T11:33:28Z")
My program boundary condition is also u = 0 on the boundary; The default setting of tgv is tgv = 1e30, but in fact, according to the obtained finite element solution, the value on the boundary is not equal to 0. --- ## [Complex number field](https://community.freefem.org/t/complex-number-field/1630)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 7\ **Last updated:** [April 2, 2022, 11:25am UTC](https://community.freefem.org/t/complex-number-field/1630 "2022-04-02T11:25:38Z")
The inner product is defined as follows, if you take the inner product over a complex field, does the test function have to be a conjugate function, is the inner product defined the same way? --- ## [Local force Calculation using stress field](https://community.freefem.org/t/local-force-calculation-using-stress-field/1634)
**Author:** [@Markov](https://community.freefem.org/u/Markov)\ **Replies:** 3\ **Last updated:** [April 2, 2022, 10:20am UTC](https://community.freefem.org/t/local-force-calculation-using-stress-field/1634 "2022-04-02T10:20:08Z")
Hello, I would like to calculate the local force vector using a stress field of the size of (0, Vh). Assuming that the stress field is already projected on to the x, y and z components (so I have three stress components… --- ## [Initialisation in different regions](https://community.freefem.org/t/initialisation-in-different-regions/1606)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 2\ **Last updated:** [April 2, 2022, 6:09am UTC](https://community.freefem.org/t/initialisation-in-different-regions/1606 "2022-04-02T06:09:57Z")
Dear all, Say mesh Th; int fluid=Th(x0,y0).region, solid=Th(x1,y1).region; fespace Vh(Th,P1); Vh phi; How can we initialise phi=0 in the fluid region, while phi=1 in the solid region? --- ## [Constraining a specific element(s) in P0 space](https://community.freefem.org/t/constraining-a-specific-element-s-in-p0-space/1633)
**Author:** [@gbwalton](https://community.freefem.org/u/gbwalton)\ **Replies:** 5\ **Last updated:** [March 30, 2022, 1:50pm UTC](https://community.freefem.org/t/constraining-a-specific-element-s-in-p0-space/1633 "2022-03-30T13:50:23Z")
Hi all, Is it possible to constrain a specific elements (or elements) as a Dirichlet reference value using P0 space? I am planning on using the iterative solvers within the PETSc library, so this doesn’t give me the opt… --- ## [Order of time convergence](https://community.freefem.org/t/order-of-time-convergence/1434)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 1\ **Last updated:** [March 30, 2022, 9:20am UTC](https://community.freefem.org/t/order-of-time-convergence/1434 "2022-03-30T09:20:26Z")
The procedure of time convergence order is as follows, but this procedure is not wrong, the final calculation can not reach the theoretical second order, only the first order, why? real lambda=0.5; real Tf=0.5; real … --- ## [PC failed due to FACTOR\_OUTMEMORY](https://community.freefem.org/t/pc-failed-due-to-factor-outmemory/1593)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 10\ **Last updated:** [March 29, 2022, 6:44pm UTC](https://community.freefem.org/t/pc-failed-due-to-factor-outmemory/1593 "2022-03-29T18:44:52Z")
Hello, I encountered the following problem when running FreeFree+±mpi (load “PETSc-complex” ) : set(A, sparams =“-pc\_type lu -pc\_factor\_mat\_solver\_type mumps -ksp\_converged\_reason”); Linear solve did not converge d… --- ## [Defining a boundary](https://community.freefem.org/t/defining-a-boundary/1628)
**Author:** [@Jamal](https://community.freefem.org/u/Jamal)\ **Replies:** 2\ **Last updated:** [March 27, 2022, 8:55am UTC](https://community.freefem.org/t/defining-a-boundary/1628 "2022-03-27T08:55:37Z")
hello everyone How to define the border \\gamma(x) with the function border + buildmesh in freefem ? --- ## [How to generate Brownian motion/ Wiener process in Freefem](https://community.freefem.org/t/how-to-generate-brownian-motion-wiener-process-in-freefem/268)
**Author:** [@lietvo](https://community.freefem.org/u/lietvo)\ **Replies:** 1\ **Last updated:** [March 26, 2022, 8:38am UTC](https://community.freefem.org/t/how-to-generate-brownian-motion-wiener-process-in-freefem/268 "2022-03-26T08:38:01Z")
Hello everyone, I just wonder if there is any way to generate Brownian motion in Freefem? I am working on a numerical stochastic problem which require to discretize the Brownian motion/Wiener process but I don’t see Fre… --- ## [Implementing new finite element in FreeFEM](https://community.freefem.org/t/implementing-new-finite-element-in-freefem/1602)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 11\ **Last updated:** [March 25, 2022, 3:30pm UTC](https://community.freefem.org/t/implementing-new-finite-element-in-freefem/1602 "2022-03-25T15:30:13Z")
Hello all, I would like to have some feedback about implementing new finite element in FreeFEM. How difficult and how long it is to implement new finite element (in particular non conforming) in FreeFEM ? For anyone w… --- ## [Periodic plus a value BC](https://community.freefem.org/t/periodic-plus-a-value-bc/1610)
**Author:** [@mahdi](https://community.freefem.org/u/mahdi)\ **Replies:** 2\ **Last updated:** [March 25, 2022, 9:57am UTC](https://community.freefem.org/t/periodic-plus-a-value-bc/1610 "2022-03-25T09:57:32Z")
Dear Fellows! I am trying to find a Boundary condition where the value on boundary A is equal to the values of B plus a constant. More like a Periodic BC where the value on B is A+const. Any thoughts or ideas are since… --- ## [Time dependent non linear problem](https://community.freefem.org/t/time-dependent-non-linear-problem/1623)
**Author:** [@jeremie](https://community.freefem.org/u/jeremie)\ **Replies:** 1\ **Last updated:** [March 24, 2022, 4:42pm UTC](https://community.freefem.org/t/time-dependent-non-linear-problem/1623 "2022-03-24T16:42:10Z")
Hello, In FreeFEM, is it possible to deal with a time dependent non linear problem like this one : \\nabla^2 A = - \\sigma(dA/dt) \* dA/dt with sigma, a non linear function. I saw that I must use a uold variable for the… --- ## [Anisotropic mesh adaptation](https://community.freefem.org/t/anisotropic-mesh-adaptation/1622)
**Author:** [@Trophime](https://community.freefem.org/u/Trophime)\ **Replies:** 3\ **Last updated:** [March 24, 2022, 4:35pm UTC](https://community.freefem.org/t/anisotropic-mesh-adaptation/1622 "2022-03-24T16:35:27Z")
Hi, I would like to run a kind of parabolic pde with anisotropic mesh adaption using a Hessian based metric. For static problem, I guess I can start from CornerLap.edp. Is there any example available for transient pb t… --- ## [Pressure boundary condition](https://community.freefem.org/t/pressure-boundary-condition/1620)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 1\ **Last updated:** [March 24, 2022, 2:25pm UTC](https://community.freefem.org/t/pressure-boundary-condition/1620 "2022-03-24T14:25:44Z")
Dear all I have a basic question. In Freefem++ the equations are solved in matrix-forming method which is different with time stepping method. As I got from Navier-Stokes example in tutorial, the pressure is modelled by… --- ## [GMSH: issue to load small element](https://community.freefem.org/t/gmsh-issue-to-load-small-element/1618)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 2\ **Last updated:** [March 23, 2022, 6:13am UTC](https://community.freefem.org/t/gmsh-issue-to-load-small-element/1618 "2022-03-23T06:13:09Z")
Hello all, It seems that GMSH (with gmshload) cannot load triangle whose the measure is smaller than 1e-8. Triangles 40 1227 127 54 mes=4.64389e-09 bug : mes \< 1e-8 ! Had someone already faced the same issue ? And h… --- ## [Thick Plate Model: Finite Elements](https://community.freefem.org/t/thick-plate-model-finite-elements/1615)
**Author:** [@AntoniJ](https://community.freefem.org/u/AntoniJ)\ **Replies:** 0\ **Last updated:** [March 21, 2022, 4:38pm UTC](https://community.freefem.org/t/thick-plate-model-finite-elements/1615 "2022-03-21T16:38:38Z")
Hello, I am trying to solve a bending problem for 2D Mindlin plates and I am not sure what elements to use. A naive approach was to use P2 elements for the vertical displacement and P1 elements for the rotations, but wi… --- ## [Tmeprature dependent properties](https://community.freefem.org/t/tmeprature-dependent-properties/1614)
**Author:** [@Mohsen](https://community.freefem.org/u/Mohsen)\ **Replies:** 0\ **Last updated:** [March 21, 2022, 1:00pm UTC](https://community.freefem.org/t/tmeprature-dependent-properties/1614 "2022-03-21T13:00:14Z")
Hello I am wondering how I can define a temeparture dependent properties? Does anyone have any simple sample to share with me? Thank you in advance --- ## [Solution error using buildmesh](https://community.freefem.org/t/solution-error-using-buildmesh/1612)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 0\ **Last updated:** [March 20, 2022, 12:59pm UTC](https://community.freefem.org/t/solution-error-using-buildmesh/1612 "2022-03-20T12:59:06Z")
In this code, I used the following code to build a local mesh real\[int, int\] nodes = \[\[coordX0, coordY0\], \[coordX1,coordY1\], \[coordX2, coordY2\]\]; //cout \<\< nodes \<\< "\\n"; border f0(t=0,1){… --- ## [3Dimensional domain generation and solving](https://community.freefem.org/t/3dimensional-domain-generation-and-solving/1611)
**Author:** [@vigneswar](https://community.freefem.org/u/vigneswar)\ **Replies:** 0\ **Last updated:** [March 19, 2022, 5:52pm UTC](https://community.freefem.org/t/3dimensional-domain-generation-and-solving/1611 "2022-03-19T17:52:09Z")
Hi guys. New to FreeFem and FEA in general. I wanted to create a 3-dimensional domain and then solve the Helmholtz equation pde. I have read the documentation, but a general 3D pde solving is not mentioned/is not clear? … --- ## [Define an Integral on R](https://community.freefem.org/t/define-an-integral-on-r/1609)
**Author:** [@Aicha](https://community.freefem.org/u/Aicha)\ **Replies:** 0\ **Last updated:** [March 17, 2022, 1:06pm UTC](https://community.freefem.org/t/define-an-integral-on-r/1609 "2022-03-17T13:06:22Z")
Hi, how we can define the function \\int\_{-\\infty}^{+\\infty} \\exp(I(t,x)) dx using FF++? Best regards --- ## [Error umpfack umfpack\_di\_numeric status 1](https://community.freefem.org/t/error-umpfack-umfpack-di-numeric-status-1/1600)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 2\ **Last updated:** [March 15, 2022, 11:14pm UTC](https://community.freefem.org/t/error-umpfack-umfpack-di-numeric-status-1/1600 "2022-03-15T23:14:36Z")
I have the following code: //---------------------------------------------------Solving for etaf varf ahKf(etafK, varphi) = int2d(Th\[K\])(kappa\*grad(etafK)'\*grad(varphi)); varf fhKf(etafK, varphi) = int2d… --- ## [Time harmonic induction heating problem](https://community.freefem.org/t/time-harmonic-induction-heating-problem/1427)
**Author:** [@altar31](https://community.freefem.org/u/altar31)\ **Replies:** 10\ **Last updated:** [March 15, 2022, 3:22pm UTC](https://community.freefem.org/t/time-harmonic-induction-heating-problem/1427 "2022-03-15T15:22:55Z")
Time harmonic induction heating problem (2D) Hi all, I’m Damien, a French engineer, currently in my last year of Ph.D. (hoping to defend it in October 2022). I’m trying to solve a 2d induction heating problem (magnetod… --- ## [Additive Schwarz method](https://community.freefem.org/t/additive-schwarz-method/1598)
**Author:** [@AbuAzzan](https://community.freefem.org/u/AbuAzzan)\ **Replies:** 0\ **Last updated:** [March 14, 2022, 7:00am UTC](https://community.freefem.org/t/additive-schwarz-method/1598 "2022-03-14T07:00:21Z")
Hi to all of you. First, I would like to thank all of you for sharing your enriching experience with us. I found a good and easy example of the Schwarz alternating method in the FreeFEM++ documentation (V4.6) for a lin… --- ## [Mesh from vector](https://community.freefem.org/t/mesh-from-vector/1595)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 1\ **Last updated:** [March 13, 2022, 11:20am UTC](https://community.freefem.org/t/mesh-from-vector/1595 "2022-03-13T11:20:21Z")
I have the following code, what am I doing wrong? //------------------Global Mesh--------------------- mesh calP = square(2,2); int NbTriangles = calP.nt; //number of triangles int NbVertices = calP.nv; //number of ver… --- ## [How to Plot Field Lines](https://community.freefem.org/t/how-to-plot-field-lines/1552)
**Author:** [@willrey](https://community.freefem.org/u/willrey)\ **Replies:** 2\ **Last updated:** [March 11, 2022, 1:08pm UTC](https://community.freefem.org/t/how-to-plot-field-lines/1552 "2022-03-11T13:08:30Z")
Hello, I’m comfortable with using the plot function to visualise the potential over a field, but how can I plot the field lines (perpendicular to the equipotentials, so that I can take a closer look at the flux paths)? … --- ## [Change boundary labels](https://community.freefem.org/t/change-boundary-labels/1590)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 1\ **Last updated:** [March 11, 2022, 1:01pm UTC](https://community.freefem.org/t/change-boundary-labels/1590 "2022-03-11T13:01:15Z")
Hi there, so, I’m trying to change boundary labels. I have a global mesh with 8 triangles and in each triangle I’m building local meshs Th\[i\], where i represents the current global element. For now, my local mesh consist… --- ## [Heaviside function integration](https://community.freefem.org/t/heaviside-function-integration/1584)
**Author:** [@ygorschka](https://community.freefem.org/u/ygorschka)\ **Replies:** 6\ **Last updated:** [March 10, 2022, 1:32pm UTC](https://community.freefem.org/t/heaviside-function-integration/1584 "2022-03-10T13:32:17Z")
Dear all, I try to integrate (H o u(x))\*v where H is Heaviside function in a 2D mesh by using: Uh(Th, P1); varf a(uu,vv) = int2d(Th)((uu == 0. ? 0.5 : (uu\>0. ? 1. : 0.))\*vv); matrix Ah = a(Uh,Uh); However, Freefem r… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=47) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=49)