Encountered the RuntimeError when solving the PDE

[dokken]

You can increase the maximum number of iterations in your non-linear solver, see:

How to increase maximum number of iterations?

See the following example: from dolfin import * # Set up some simple demonstration nonlinear problem: mesh = UnitIntervalMesh(10) V = FunctionSpace(mesh,"CG",1) u = Function(V) v = TestFunction(V) x = SpatialCoordinate(mesh) F = (u+1)**2*dot(grad(u),grad(v))*dx + u*v*dx - sin(x[0])*v*dx problem = NonlinearVariationalProblem(F,u,J=derivative(F,u),bcs=[]) # Create solver: solver = NonlinearVariationalSolver(problem) stype = 'newton' solver.parameters['nonlinear_solver']=stype sprms = solver.par…

For further questions, I strongly suggest that you provide a minimal reproducible example.