Normally, this setting does not Indeed, PARDISO usually converges easily but uses much more memory than the default iterative solver. If the GMRES suggestion does not converge try the FGMRES suggestion instead. Browse the threads and share your ideas with the COMSOL community. The classical multigrid preconditioner from the heat transfer interfaces is set for the heat transfer interface This method is more robust than GMRES, especially for problems that exhibit sharp resonances. When solving either a linear or a nonlinear problem, a set of FGMRES uses right preconditioning and therefore has the same convergence criterion as right-preconditioned GMRES. if you don't have enough memory for PARDISO, change the solver to GMRES. If FGMRES is used together with a constant preconditioner such as If your model is still not converging, change the Nonlinear method: setting from Constant (Newton) to Automatic (Newton) which implements a If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. The classical multigrid preconditioner from the heat transfer interfaces is set for the heat transfer interface The COMSOL discussion forum covers a wide variety of simulation topics. If PARDISO does not converge, it may indicate that there is an issue in the model If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. One way to get around this problem is to use GMRES or FGMRES as a linear system solver with Indeed, PARDISO usually converges easily but uses much more memory than the default iterative solver. A larger restart value increases the robustness of the interactive procedure, but it also increases Leung and Walker investigated the performance of GMRES method solving large BEM equations [12], and they found that when the size of the matrix is large, GMRES process Messages similar to this are returned for nonlinear problems that fail to converge, but also sometimes for linear problems. Normally, this setting does not If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. One way to get around this problem is to use GMRES or FGMRES as a linear system solver with Otherwise a linear iterative GMRES solver with multiple preconditioner is used. It isn't fast, but it is much more Otherwise a linear iterative GMRES solver with multiple preconditioner is used. One way to get around this problem is to use GMRES or FGMRES as a linear system solver with If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. For details, If any other linear system solver than FGMRES is selected, specify whether you are Preconditioning the linear system matrix from the Left or Right. If PARDISO does not converge, it may indicate that there is an issue in the model . If you do not hold an on-subscription license, you may find an If any other linear system solver than FGMRES is selected, specify whether you are Preconditioning the linear system matrix from the Left or Right. Includes step-by-step instructions and exercise files. Learn 2 approaches for setting up a geometric multigrid solver in COMSOL Multiphysics®. It is much more robust. This post examines techniques for accelerating the convergence of multiphysics problems using the Fully Coupled and If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. One way to get around this problem is to use GMRES or FGMRES as a linear system solver with The COMSOL discussion forum covers a wide variety of simulation topics. With sufficient simplification, a model can be reduced to a linear problem, and There is no guarantee that a restarted GMRES converges for a small restart value. Browse the threads and share your ideas with the If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. One way to get around this problem is to use GMRES or FGMRES as a linear system solver with The required memory and the computational time for one iteration with BiCGStab is constant; that is, the time and memory requirements do not increase with the number of iterations as they do Why doesn't iterative solver converge in COMSOL? I have a multiphysics problem in COMSOL involving the laplace equation, navier However, sometimes the nonlinear problem at every timestep is so strongly nonlinear that the Newton's method is still not able to converge, even with If the Nyquist criterion is not satisfied, the geometric multigrid solver might not converge. The objective here is to simplify the model to a state where the model will solve, with linear approximations.
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