Le 22 nov. 2013 à 10:25, Anders Logg <[email protected]> a écrit :
>
>
>> However, the issue is larger than that.
>> Many other parameters are not passed, although existing in snes and
>> newton_solver.
>>
>> For example it is not possible to set the tolerance or the max iterations of
>> the krylov_solver used in the newton or snes iterations, which is very bad
>> in my opinion.
>> I proposed a (ugly) fix some time ago which was declined (
>> https://bitbucket.org/fenics-project/dolfin/pull-request/34/updating-of-ksp-parameters-in/diff
>> ).
>> However I think that something must be done, because many parameters are
>> shown and modifiable, but they are not taken into account.
>
> Are you sure? These lines from NewtonSolver.cpp should take care of that:
>
> // Set parameters for linear solver
> if (solver_type == "direct" || solver_type == "lu")
> _solver->update_parameters(parameters("lu_solver"));
> else if (solver_type == "iterative")
> _solver->update_parameters(parameters("krylov_solver"));
> else
> warning("Unable to set parameters for linear solver type \"%s\".",
> solver_type.c_str());
>
As a matter of fact when you try to set the options of the krylov solver they
do not work.
Please, check with the example of demo_hyperelasticity reported in the previous
message.
For example with par_new.krylov_solver["monitor_convergence"] = True one
expects the output of the krylov solver iterations.
I agree that the lines you cite are supposed to do the work. However, in
practice, it is not evident to track what
_solver->update_parameters(parameters("krylov_solver"))
does: _solver is a GenericLinearSolver and there are several wrapping before
arriving to KrylovSolver. I suspect that there is a problem in one of those
passages.
>
>
>> To test on newton_solver, consider the following modify version of
>> demo_hyperelasticity, where par_new.krylov_solver are ignored:
>>
>> from dolfin import *
>>
>> # Optimization options for the form compiler
>> parameters["form_compiler"]["cpp_optimize"] = True
>> ffc_options = {"optimize": True, \
>> "eliminate_zeros": True, \
>> "precompute_basis_const": True, \
>> "precompute_ip_const": True}
>>
>> # Create mesh and define function space
>> mesh = UnitCubeMesh(24, 16, 16)
>> V = VectorFunctionSpace(mesh, "Lagrange", 1)
>>
>> # Mark boundary subdomians
>> left = CompiledSubDomain("near(x[0], side) && on_boundary", side = 0.0)
>> right = CompiledSubDomain("near(x[0], side) && on_boundary", side = 1.0)
>>
>> # Define Dirichlet boundary (x = 0 or x = 1)
>> c = Expression(("0.0", "0.0", "0.0"))
>> r = Expression(("scale*0.0",
>> "scale*(y0 + (x[1] - y0)*cos(theta) - (x[2] - z0)*sin(theta)
>> - x[1])",
>> "scale*(z0 + (x[1] - y0)*sin(theta) + (x[2] - z0)*cos(theta)
>> - x[2])"),
>> scale = 0.5, y0 = 0.5, z0 = 0.5, theta = pi/3)
>>
>> bcl = DirichletBC(V, c, left)
>> bcr = DirichletBC(V, r, right)
>> bcs = [bcl, bcr]
>>
>> # Define functions
>> du = TrialFunction(V) # Incremental displacement
>> v = TestFunction(V) # Test function
>> u = Function(V) # Displacement from previous iteration
>> B = Constant((0.0, -0.5, 0.0)) # Body force per unit volume
>> T = Constant((0.1, 0.0, 0.0)) # Traction force on the boundary
>>
>> # Kinematics
>> I = Identity(V.cell().d) # Identity tensor
>> F = I + grad(u) # Deformation gradient
>> C = F.T*F # Right Cauchy-Green tensor
>>
>> # Invariants of deformation tensors
>> Ic = tr(C)
>> J = det(F)
>>
>> # Elasticity parameters
>> E, nu = 10.0, 0.3
>> mu, lmbda = Constant(E/(2*(1 + nu))), Constant(E*nu/((1 + nu)*(1 - 2*nu)))
>>
>> # Stored strain energy density (compressible neo-Hookean model)
>> psi = (mu/2)*(Ic - 3) - mu*ln(J) + (lmbda/2)*(ln(J))**2
>>
>> # Total potential energy
>> Pi = psi*dx - dot(B, u)*dx - dot(T, u)*ds
>>
>> # Compute first variation of Pi (directional derivative about u in the
>> direction of v)
>> F = derivative(Pi, u, v)
>>
>> # Compute Jacobian of F
>> J = derivative(F, u, du)
>>
>> # Solve variational problem
>> problem =
>> NonlinearVariationalProblem(F,u,bcs,J,form_compiler_parameters=ffc_options)
>> solver = NonlinearVariationalSolver(problem)
>> par_new = solver.parameters.newton_solver
>> par_new.linear_solver = "gmres"
>> par_new.preconditioner = "amg"
>> par_new.krylov_solver["report"] = True
>> par_new.krylov_solver["monitor_convergence"] = True
>> par_new.krylov_solver["maximum_iterations"] = 5
>> info(par_new, True)
>> solver.solve()
>>
>>
>>
>>
>>
>> Corrado Maurini
>> [email protected]
>>
>>
>>
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>> http://fenicsproject.org/mailman/listinfo/fenics
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