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## [Libmesh-users] Nonlinear equation

 [Libmesh-users] Nonlinear equation From: John Peterson - 2005-02-08 14:42:22 ```Michael Povolotskyi writes: > Hello everybody, I'm solving a non-linear Poisson equation, > i.e. Poisson equation with a non-linear right hand side function. > I'd like to use the NonlinearImplicitSystem class that contains an > interface to the nonlinear solver of PETSc. As fas as I can see > from NonlinearSolver class documentation a user has to define two > functions with a particular interface: > > These functions should be able to access the information about > mesh. It is not clear for me how do this. Hi, The NonlinearImplicitSystem inherits the get_mesh() method from the System base class. Note that the right way to use Systems is inside an EquationSystems object, as is done in the examples. -John ```

 [Libmesh-users] Nonlinear equation From: Michael Povolotskyi - 2005-02-08 12:29:42 ```Hello everybody, I'm solving a non-linear Poisson equation, i.e. Poisson equation with a non-linear right hand side function. I'd like to use the NonlinearImplicitSystem class that contains an interface to the nonlinear solver of PETSc. As fas as I can see from NonlinearSolver class documentation a user has to define two functions with a particular interface: void(* residual )(const NumericVector< Number > &X, NumericVector< Number > &R) void(* jacobian )(const NumericVector< Number > &X, SparseMatrix< Number > &J) These functions should be able to access the information about mesh. It is not clear for me how do this. Thank you very much, Michael. -- ------------------------------------------------------------ Michael Povolotskyi, Ph.D. University of Rome "Tor Vergata" Department of Electronic Engineering Viale Politecnico, 1 - 00133 Rome - Italy Phone + 39 06 72597367 Fax + 39 06 2020519 http://www.optolab.uniroma2.it/pages/moshe/moshe.html ------------------------------------------------------------- ```
 [Libmesh-users] Nonlinear equation From: John Peterson - 2005-02-08 14:42:22 ```Michael Povolotskyi writes: > Hello everybody, I'm solving a non-linear Poisson equation, > i.e. Poisson equation with a non-linear right hand side function. > I'd like to use the NonlinearImplicitSystem class that contains an > interface to the nonlinear solver of PETSc. As fas as I can see > from NonlinearSolver class documentation a user has to define two > functions with a particular interface: > > These functions should be able to access the information about > mesh. It is not clear for me how do this. Hi, The NonlinearImplicitSystem inherits the get_mesh() method from the System base class. Note that the right way to use Systems is inside an EquationSystems object, as is done in the examples. -John ```