Mass lumping in time dependent problem

[kamensky]

You would probably need to define a custom NonlinearProblem subclass, as demonstrated here:

Callbacks on Newton solver

You can create a custom nonlinear problem instance that allows arbitrary code to execute while forming the residual and/or Jacobian. See the following example: from dolfin import * mesh = UnitSquareMesh(10,10) V = FunctionSpace(mesh,"Lagrange",1) u = Function(V) v = TestFunction(V) x = SpatialCoordinate(mesh) f = x[0]*x[1] res = (1.0+u*u)*inner(grad(u),grad(v))*dx + inner(u,v)*dx - inner(f,v)*dx Dres = derivative(res,u) class CustomNonlinearProblem(NonlinearProblem): def F(self,b,x): …