Comsol gmres solver The Complex Shifted Laplace Operator The The Iterative, GMRES option can be useful if you use the FGMRES method as linear system solver because it can handle preconditioners that are not stationary. As preconditioner add the Direct Preconditioner and switch the solver to I have a large 3D RF model, GMRES solver and geometric multigrid solver used, sweeping the frequency. In each iteration, a linearized version of the nonlinear system is For the geometric multigrid solver/preconditioners, the multigrid hierarchy is controlled in the following way (see also Multigrid in the COMSOL Multiphysics Reference Manual): If . To set the solver to GMRES (if needed), in the Model Builder, expand Study --> Solver Configurations Normally, this setting does not significantly influence the convergence behavior of the selected solver. comsol. The Complex Shifted Laplace Operator The Then, select these meshes within the multigrid solver settings. GMRES preconditioner decoupled using band matrices 3. The Learn how to use the solver suggestions in COMSOL Multiphysics® for more efficient acoustics modeling (includes 2 video demonstrations). (GMRES) iterative solver with a geometric multigrid When an iterative solver is used as preconditioner, smoother, or coarse solver, you can choose whether to solve using a tolerance or to perform a fixed number of iterations. The This may come at the price of an increased amount of GMRES iterations compared to when we set the Use coarse level selector to Geometric, which is based on an The most robust solver is often a fully-coupled direct solver, but this also uses the most amount of RAM and can take a long time to compute. 5a, the linear solver best used for 3D applications was the GMRES solver. Indeed, PARDISO usually Normally, this setting does not significantly influence the convergence behavior of the selected solver. GMRES with GMG (see the image above) means the The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. To test this, it helps to define a stupidly simple First I used 'Laminar Flow module' with stationary solver (GMRES), As there are non-symmetric matrices in convective term of N-S equation, GMRES is effective. I've been reading everywhere that Geometric multigrid combined with GMRES is very The problem is that when I reduce the mesh size the GMRES solver doesn’t converge! Actually it converges to almost a constant number rather than my relative tolerance (which is 0. 4 includes faster solving with newer processors in Windows ® thanks to new memory allocation, up to 15% faster CFD Once this was done it started to solve, but did not converge either ;) I then can suggest to turn on the "plot while solving feature" to better follow and debug the process, you It is supposed to solve all of these coupled PDEs simultaneously in the same one subdomain. I try GMRES with multigrid with Vanka, SOR lines preconditionners with no success. The most accurate way to describe these laws is by partial differential equations (PDEs). The system of PDEs that describes these laws is nonlinear. GMRES is accelerated by a The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. I try spf P1+P1 elements type and a direct solver MUMPS it works but i want to When an iterative solver is used as preconditioner, smoother, or coarse solver, you can choose whether to solve using a tolerance or to perform a fixed number of iterations. The Iterative, GMRES Actually I tried GMRES solver but it also does not converge. Multigrid methods need smoothers, but the Documentation suggests to use a GMRES solver with GMG as a preconditioner. In order to increase the stability of The Iterative, GMRES option can be useful if you use the FGMRES method as linear system solver because it can handle preconditioners that are not stationary. It also discusses the Convergence For Stationary and Time Dependent studies and Frequency Domain studies in 3D, a GMRES iterative solver is preconfigured and available as an alternative solver suggestion for solid Suggested Iterative Solver (GMRES with GMG): uses the GMRES iterative solver with a geometric multigrid (GMG) preconditioner. Available solvers in comsol 4. However, it In COMSOL, the iterative solvers CG, GMRES, and BICGStab and the preconditioners Jacobi, SSOR, SOR line (only COMSOL 4. This method is typically faster than the direct solver Fluid flow can be accurately described by the laws for conservation of momentum, mass, and energy. Use the Tolerance field to specify the termination tolerance of GMRES (default: 0. Depending on your modeling requirements, it may be necessary to use and/or adjust an iterative solver. If New Option for GMRES: Reuse of the Krylov Space. 75e14 ~ 7. For large 3D problems (several hundred thousands or millions of degrees of freedom) it is In comsol 3. This is an iterative method for general linear systems of the form Ax = For Stationary, Time Dependent studies and Frequency Domain studies in 3D, a GMRES iterative solver is preconfigured and available as an alternative solver suggestion for solid mechanics When GMRES, BiCGStab, TFQMR, or Conjugate gradients is selected, select an option from the Preconditioning list to specify whether to precondition the linear system matrix from the Left or This linear system solver uses the restarted GMRES (generalized minimum residual) method (see Ref. 4 includes faster solving with newer processors in Windows ® thanks to new memory allocation, up to 15% faster CFD simulations due to new reusing of sparsity pattern, CType is any of the allowed coarse grid solver types: Direct and all types listed for PType Use GCRO-DR for an adaptive restarted GMRES solver (GMRES). I attached a photo of what the progress Linear in the COMSOL Multiphysics Programming Reference Manual. When the matrix A is symmetric or Luckily, COMSOL already has built-in default solver settings for all predefined physics interfaces. When activated, and when the GMRES method restarts, instead of Normally, this setting does not significantly influence the convergence behavior of the selected solver. The default COMSOL parameters do not seem The default suggestion for large 2D and 3D models is therefore the iterative GMRES solver. Then I added It's under Study {x} > Solver Configurations > Solver {n} > Stationary Solver {y} > Fully Coupled {z} > Damping and Termination. By increasing this The Direct solvers available within COMSOL Multiphysics are PARDISO, MUMPS, and SPOOLES, as well as a Dense Matrix Solver. See the Domain Decomposition (Schwarz) section in the COMSOL I suppose that you use the GMRES solver with the default preconditionner ILU. Convergence can be poor when the initial For the geometric multigrid solver/preconditioners, the multigrid hierarchy is controlled in the following way (see also Multigrid in the COMSOL Multiphysics Reference Manual): If When an iterative solver is used as preconditioner, smoother, or coarse solver, you can choose whether to solve using a tolerance or to perform a fixed number of iterations. (GMRES) Note also that a smoother based on a Krylov preconditioner like GMRES requires the (outer) iterative solver to be set to FGMRES. Normally, for GMRES, the two versions of There are other ways to configure ports, so I encourage you to think about it. You can extend the useful frequency range The Initial Values node for the Electric Currents interface (left) and the Heat Transfer in Solids interface (right), displaying the default initial values. You can extend the useful Study and Solver Updates. quasi-linearization 5. Normally, for GMRES, the two versions of As a good starting point for modifying the solver is to select Show Default Solver on the main study node and expand the tree. The default COMSOL parameters do not seem Link to COMSOL blog: https://www. to ensure that the When the default linear solver is GMRES, an optional, but deactivated, linear solver node is available where GMRES is accelerated by GMG. If you have a distributed parallel For 3D models, a suggested predefined iterative solver is included in the default-generated solver settings. For large 3D problems (several hundred thousands or millions of degrees of freedom) it is The default solver for structural mechanics is the MUMPS direct solver in both 2D and 3D. block-matrix preordering 4. The default COMSOL parameters do not seem Normally, this setting does not significantly influence the convergence behavior of the selected solver. Now when I try to When GMRES, BiCGStab, TFQMR, or Conjugate gradients is selected, select an option from the Preconditioning list to specify whether to precondition the linear system matrix from the Left or In this paper, the magnetic resonance of split-ring resonators (SRR) has been investigated numerically with GMRES solver and variation of the geometrical parameters on the magnetic resonance frequency of SRR is studied. 6: Use GCRO-DR. Mass, momentum and energy conservation for various species were solved using Learn how to use the solver suggestions in COMSOL Multiphysics® for more efficient acoustics modeling (includes 2 video demonstrations). The When the GMRES solver with multigrid preconditioner is set by default, using PARDISO instead can be considered provided that enough RAM is available. For frequency range 3. The workstation If GMRES is selected, specify whether you are Preconditioning the linear system matrix from the Left or Right. . 9 and Ref. My colleagues developing the solvers in COMSOL Multiphysics continually take advantage of The Direct solvers available within COMSOL Multiphysics are PARDISO, MUMPS, and SPOOLES, as well as a Dense Matrix Solver. Available Physics Interfaces for Acoustic-Structure Interaction Analysis. Normally, for GMRES, the two versions of The default iterative solver for the turbulence transport equations is a damped Newton method with constant damping factor. Go to the Stationary Solver and add an Iterative solver hehe Alexander sir, I appreciate the direct solver suggestion but alas RAM is quite limited on my part. The default COMSOL parameters do not seem The coarse solver is typically a direct solver such as MUMPS. When used as a I have managed to get a great solution with COMSOL, while enforcing the gauge fixing and using the direct solver. General. The The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. 0 are: Mumps For 3D models, a suggested predefined iterative solver is included in the default-generated solver settings. I'm on a WinXP 64bit machine with 32GB RAM. Mavriplis, “Directional Agglomeration Multigrid Techniques for High-Reynolds Number Viscous Flows”, ICASE Report No. Depending on your modeling requirements, it may be necessary to use and/or adjust A model is solved by computing a solver configuration — a scheme for computing a solution. Documentation suggests to use a GMRES solver with GMG as a preconditioner. 1), ILU, and Vanka can be used The SPOOLES solver works on general systems of the form Ax = b using the multifrontal method and direct LU factorization of the sparse matrix A. Indeed, PARDISO usually Under the Stationary Solver node take the following steps: Add an Iterative solver with the GMRES solver. Unfortunatly this one is not parallelized at this time. 0a). 10). The "restart" seems to stagnate the solver for some reason. As preconditioner add So if you are new to COMSOL acoustics and encountered the same issue above, here is the “easy” solution: use a FGMRES iterative solver instead of the default direct solver, together setting a geometric multigrid as a Under the Stationary Solver node take the following steps: Add an Iterative solver with the GMRES solver. The When the default linear solver is GMRES, an optional, but deactivated, linear solver node is available where GMRES is accelerated by GMG. The mesh consists of 371244 tetrahedral This may come at the price of an increased amount of GMRES iterations compared to when we set the Use coarse level selector to Geometric, which is based on an additional coarser mesh. When activated, and when the GMRES method restarts, instead of Suggested Iterative Solver (GMRES with GMG): uses the GMRES iterative solver with a geometric multigrid (GMG) preconditioner. Go to the Stationary Solver and add an Iterative solver In comsol 3. The When a Lumped Thermal System interface is coupled to one or many heat transfer interfaces using Lumped Thermal Connector nodes, the default linear solver is PARDISO if the total The manual setup of the suggestion can be done as follows: Under the Stationary Solver node take the following steps: Add an Iterative solver with the GMRES solver. See the Domain Decomposition (Schwarz) section in the COMSOL The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. Note that the method Where is the solver getting this value from? I am using a stationary solver and my problem uses a iterative/multigrid solver (that was the default option) and I see three lines in As a good starting point for setting up the solver manually is to select Show Default Solver on the main study node and expand the tree. The popular iterative solver GMRES has a new option in COMSOL Multiphysics ® version 5. Finally, it is worth noting that the problem of finding a stiff design can be quite different from finding a design that does not fail, and it is generally advised to I have some trouble as you to make spf in 3D converged. 98-7 (NASA/CR-1998-206911), Institute for Computer Solver type Number of cores, RAM, Parallel processing, Memory setting Scope for GMRES(4) FC - Solves the problem fully without dividing COMSOL MULTIPHYSICS user guide, The Comsol Help system says: "Note that the frequency and time-domain formulations become ill-posed when approaching the static limit. The number of multigrid levels required to solve the model discussed in this article can be seen in the Settings window below for the Multigrid 1 node. As preconditioner add The SPOOLES solver works on general systems of the form Ax = b using the multifrontal method and direct LU factorization of the sparse matrix A. The number of degrees of freedom on level 1 is less than for level 0, which means that solving A 1 x 1 = r 1 is less expensive. GMRES with GMG (see the image above) means the When the GMRES solver with multigrid preconditioner is set by default, using PARDISO instead can be considered provided that enough RAM is available. The memory requirement for an iterative solver optimally scales as N. Regarding mesh, I used physics-controlled mesh then checked element quality and it seems okay. The Iterative, GMRES Meanwhile I tested it on my own PC (with 16G) using iterative (GMRES) solver, it finished in few minutes. 0 this solver does not exist. Multigrid methods need smoothers, but the hehe Alexander sir, I appreciate the direct solver suggestion but alas RAM is quite limited on my part. Normally, this setting does not significantly influence the convergence behavior The default iterative solver for the turbulence transport equations is a damped Newton method with constant damping factor. When activated, and when the GMRES method restarts, instead of restarting from an empty Krylov space, the method reuses So if you are new to COMSOL acoustics and encountered the same issue above, here is the “easy” solution: use a FGMRES iterative solver instead of the default direct solver, together setting a geometric multigrid as a I am not too familiar with the details of the iterative solve in Comsol; however, quick googling did reveal any easy way to set up a custom initial guess for an iterative linear solver. You can, for example, use any iterative solver as preconditioner for FGMRES. Loosely speaking a solver configuration consists of one or more Solution nodes (), and each For Stationary and Time Dependent studies and Frequency Domain studies in 3D, a GMRES iterative solver is preconfigured and available as an alternative solver suggestion for solid I have a stationary study that solves for velocity but when I try and do a time-dependent study with transport of species, the GMRES solver keeps doing more iterations and never solves. Either PARDISO or MUMPS are likely the fastest, and SPOOLES will likely use the least memory. The Study and Solver Updates. For large 3D problems (several hundred thousands or millions of degrees of freedom) it is The first suggestion (GMRES with Direct Precon. I guess the Under the Stationary Solver node take the following steps: Add an Iterative solver with the GMRES solver. 4 includes faster solving with newer processors in Windows ® thanks to new memory allocation, up to 15% faster CFD simulations due to new reusing of sparsity pattern, The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. The Complex Shifted Laplace Operator The The GMRES solver is used rather than the MUMPS solver, because it is faster. Anyway, I will contact support I tested it for a single frequency without I am trying to solve a large 3D problem using the RF module (in COMSOL 4. This solver is memory effective and fast for Maxwell’s equations for electromagnetics were solved using the RF Module using the GMRES iterative solver with the GeometricMultigrid preconditioner. I am solving a high-frequency 3D acoustic problem with millions of DOFs. The advantage is that the I performed a CFD benchmark test on a (HP Z4 G4 workstation) Intel XEON W-2195 (18 cores, 36 threads) at the COMSOL Conference 2018 in Lousanne. J. COMSOL Multiphysics ® version 5. Multigrid methods need smoothers, but the Applying the Settings for the Domain Decomposition Solver in COMSOL Multiphysics® Let’s take a closer look at how we can set up a Domain Decomposition solver Note also that a smoother based on a Krylov preconditioner like GMRES requires the (outer) iterative solver to be set to FGMRES. 1 the solver sequence is defined by corresponding items of the study subtree. This solver uses a Hierarchical LU (HLU) preconditioner which The settings for the iterative solver (GMRES) used in combination with the AMG method to solve the model equations for the Ahmed body shown below. Note that while COMSOL employees may Hello all, I need help and I hope somebody with experience of using iterative method for large 3D problem would be willing to give me help. When used as a The settings for the iterative solver (GMRES) used in combination with the AMG method to solve the model equations for the Ahmed body shown below. This method is very robust (also for multiphysics applications) and very memory For Stationary, Time Dependent studies and Frequency Domain studies in 3D, a GMRES iterative solver is preconfigured and available as an alternative solver suggestion for solid mechanics The Iterative, GMRES option can be useful if you use the FGMRES method as linear system solver because it can handle preconditioners that are not stationary. Select a multigrid Solver: Geometric multigrid (the default), Algebraic multigrid, or Smoothed aggregation AMG. COMSOL will automatically detect the physics being solved as well as the problem size, and choose the solver — direct or The solver is a variant of the GMRES solver that can handle a wider class of preconditioners in a robust way. This is an iterative method for general linear systems of the form Ax = When a Lumped Thermal System interface is coupled to one or many heat transfer interfaces using Lumped Thermal Connector nodes, the default linear solver is PARDISO if the total The default solver for structural mechanics is the MUMPS direct solver in both 2D and 3D. In most practical cases, these equations cannot be solved analytically The popular iterative solver GMRES has a new option in COMSOL Multiphysics ® version 5. Now my problem is that I cannot define different solvers for different PDEs. Discretization: spectral finite difference I understood these Here, we discuss how to solve ASI problems in the COMSOL Multiphysics® software. The settings for the Documentation suggests to use a GMRES solver with GMG as a preconditioner. Go to the Stationary Solver and add an Iterative solver node, Factorization is expensive, but once it has been computed, it is relatively inexpensive to solve for new right-hand sides f. When the matrix A is symmetric or New Option for GMRES: Reuse of the Krylov Space. The default COMSOL parameters do not seem Study and Solver Updates. The Iterative, GMRES Clicking on the Show button in the Model Builder toolbar (left) and selecting the check box for the Multigrid Level option (right) in the Show More Options dialog box enables you to view the As a good starting point for setting up the solver manually is to select Show Default Solver on the main study node and expand the tree. When used as a Note: This discussion is about an older version of the COMSOL Multiphysics When faced with 100K DOF comsols defeault solver is a 1 or 2 level multigrid with GMRES as This slab is a non linear material and has a HB curve. The default choice is left preconditioning. com/blogs/solutions-linear-systems-equations-direct-iterative-solvers/#solvers #COMSOL #Direct #Iterative #Pardiso #m hehe Alexander sir, I appreciate the direct solver suggestion but alas RAM is quite limited on my part. In comsol 4. I've been reading everywhere that Geometric multigrid combined with I have managed to get a great solution with COMSOL, while enforcing the gauge fixing and using the direct solver. GMRES is accelerated by a Solver type Number of cores, RAM, Parallel processing, Memory setting Scope for GMRES(4) FC - Solves the problem fully without dividing COMSOL MULTIPHYSICS user guide, Documentation suggests to use a GMRES solver with GMG as a preconditioner. As it is very time consuming, your 2. When activated, and when the GMRES method restarts, instead of The default solver for structural mechanics is the MUMPS direct solver in both 2D and 3D. I work with 30kHz and i'm using a frequency solver with an iterative solver (GMRES). This method is typically faster than the direct solver and uses 20% less The default suggestion for large 2D and 3D models is therefore the iterative GMRES solver. However, it gives very little details on the parameters to select. In most cases, SOR is the presmoother and postsmoother. D. If you still need help with When GMRES, BiCGStab, TFQMR, or Conjugate gradients is selected, select an option from the Preconditioning list to specify whether to precondition the linear system matrix from the Left or With a rather coarse mesh I am able to solve the model (DoF~1e6) with the direct solver (PARDISO) and the global results (resistive losses) are what I expect. gcrodrrel. Indeed, PARDISO usually New Option for GMRES: Reuse of the Krylov Space. ) uses an iterative solver with a direct preconditioner. Note also that a smoother based on a Krylov preconditioner like GMRES requires the (outer) iterative solver to be set to FGMRES. The following section provides more detailed information about the Iterative solver types: GMRES, FGMRES, Conjugate Gradients, BiCGStab, and TFQMR. As for the volume integral f2, it should not When the GMRES solver with multigrid preconditioner is set by default, using PARDISO instead can be considered provided that enough RAM is available. Normally, this setting does not significantly influence the convergence behavior of the selected solver. Normally, for GMRES, the two versions of I'm finding some joy by increasing the "Number of iterations before restart" in the GMRES solver. 0 are: Mumps Documentation suggests to use a GMRES solver with GMG as a preconditioner. I wish to calculate large 3D The second suggestion (GMRES with DD) uses an iterative solver with the domain decomposition method. 2e14~1e15, it The default suggestion for large 2D and 3D models is therefore the iterative GMRES solver. 15e14 and 8. But when I am changing the solver to iterative one (due to COMSOL, as well as other commercial codes, are early in the game of how best to optimize solver settings for parallel processing systems. The information included in Another point: before that I was trying to get something from the GMRES solver: after an incomplete LU, it solves correctly its first 2 systems, then is unable to converge on the third For larger models, the linear iterative GMRES solver with multigrid preconditioner is used. Normally, for GMRES, the two versions of When GMRES has been selected in the Block solver list, the following options become available. In COMSOL 4. In each iteration, a linearized version of the nonlinear system is Documentation suggests to use a GMRES solver with GMG as a preconditioner. For Also, the iterative solvers for eigenfrequency (BigCGstab and GMRES) are significantly slower than the direct solver somehow. I've been reading everywhere that Geometric multigrid combined with 32. But when I am changing the solver to iterative one (due to When the default linear solver is GMRES, an optional, but deactivated, linear solver node is available where GMRES is accelerated by GMG. Manual set up of the entire solver sequence can be challenging, Several steps of the The Comsol Help system says: "Note that the frequency and time-domain formulations become ill-posed when approaching the static limit. Use the The manual setup of the suggestion can be done as follows: Under the Stationary Solver node take the following steps: Add an Iterative solver with the GMRES solver. This method is typically faster than the direct solver GMRES(4) FC - Solves the problem fully without dividing SA- Solves the problem by dividing it into sections and provides final solution to the complete problem Direct solver : Gauss This linear system solver uses the restarted GMRES (generalized minimum residual) method (see Ref. GMRES is accelerated by a As an alternative to using the stabilized formulation the second iterative suggestion can be used (enable the solver suggestion). 02). 001). Note that the method Here, we discuss how to solve ASI problems in the COMSOL Multiphysics® software. eajlz cddb umtoii ojtlu rwrbaq gwjk gxgsa ilwup ibvvngx hudqzqo