dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Jul 02, 2009 at 03:04:34PM +0200, Johan Hake wrote:
> On Thursday 02 July 2009 14:45:03 Anders Logg wrote:
> > On Thu, Jul 02, 2009 at 02:31:32PM +0200, DOLFIN wrote:
> > > changeset:   6398:9a984c7459ed594858b34aac700338a1ea2e6b67
> > > parent:      6396:ea89145d8ec9846d689122b1b2cea5c964c09f00
> > > user:        Anders Logg <logg@xxxxxxxxx>
> > > date:        Thu Jul 02 14:31:14 2009 +0200
> > > files:       bench/ode/reaction/bench.log bench/ode/reaction/bench.py
> > > demo/ode/collection/cpp/main.cpp demo/ode/courtemanche/cpp/main.cpp
> > > demo/ode/harmonic/cpp/main.cpp demo/ode/lorenz/cpp/main.cpp
> > > demo/ode/reaction/cpp/main.cpp demo/ode/tentusscher/cpp/main.cpp
> > > demo/ode/tentusscher/cpp/tentusscher.h
> > > demo/pde/cahn-hilliard/cpp/main.cpp demo/pde/dg/poisson/cpp/main.cpp
> > > demo/pde/elasticity/cpp/main.cpp demo/pde/stokes/stabilized/cpp/main.cpp
> > > demo/pde/stokes/taylor-hood/cpp/main.cpp dolfin/common/Variable.cpp
> > > dolfin/common/Variable.h dolfin/fem/VariationalProblem.cpp
> > > dolfin/fem/VariationalProblem.h dolfin/la/GenericLinearSolver.h
> > > dolfin/la/KrylovSolver.h dolfin/la/LUSolver.h dolfin/la/LinearSolver.cpp
> > > dolfin/la/LinearSolver.h dolfin/la/PETScKrylovSolver.cpp
> > > dolfin/la/PETScLUSolver.cpp dolfin/la/PETScLUSolver.h
> > > dolfin/la/SingularSolver.cpp dolfin/la/SingularSolver.h
> > > dolfin/la/uBLASKrylovSolver.cpp dolfin/la/uBLASKrylovSolver.h
> > > dolfin/main/SubSystemsManager.cpp dolfin/main/SubSystemsManager.h
> > > dolfin/mesh/MeshFunction.h dolfin/nls/NewtonSolver.cpp
> > > dolfin/nls/NewtonSolver.h dolfin/ode/Adaptivity.cpp
> > > dolfin/ode/Dependencies.cpp dolfin/ode/Dual.cpp dolfin/ode/GMPObject.h
> > > dolfin/ode/MonoAdaptiveFixedPointSolver.cpp
> > > dolfin/ode/MonoAdaptiveNewtonSolver.cpp
> > > dolfin/ode/MonoAdaptiveTimeSlab.cpp dolfin/ode/MonoAdaptivity.cpp
> > > dolfin/ode/MultiAdaptiveFixedPointSolver.cpp
> > > dolfin/ode/MultiAdaptiveNewtonSolver.cpp
> > > dolfin/ode/MultiAdaptiveTimeSlab.cpp dolfin/ode/MultiAdaptivity.cpp
> > > dolfin/ode/ODE.cpp dolfin/ode/ODE.h dolfin/ode/ODESolution.cpp
> > > dolfin/ode/ODESolver.cpp dolfin/ode/Partition.cpp dolfin/ode/TimeSlab.cpp
> > > dolfin/ode/TimeSlabSolver.cpp dolfin/ode/TimeStepper.cpp
> > > dolfin/parameter/DefaultParameters.h dolfin/parameter/NewParameter.cpp
> > > dolfin/parameter/NewParameter.h dolfin/parameter/NewParameters.cpp
> > > dolfin/parameter/NewParameters.h dolfin/swig/dolfin_shared_ptr_classes.i
> > > dolfin/swig/ignores.i description:
> > > Work on transition to new parameter system. Used now in most places
> > > some work remains. Global parameters still handled by the old system.
> 
> Nice work!

Not so nice. I managed to push some changes I didn't intend to push
just yet which introduces some new bugs. It should be fixed in a
little while. Update: just pushed.

> This commit has to result in a Super Nova in the FENICS movie ;)

That's my plan. But in general, I try to avoid supernovas since they
are potentially hard to merge. :-)

> > Some comments on the status of the transition:
> >
> > 1. All C++ demos and unit tests seem ok and most Python demos, but
> > some of them crash (segmentation fault). I haven't tracked this down
> > yet. Any suggestions are welcome.
> >
> > 2. Default values for all parameters are set in functions named
> > default_parameters(). For visibility, this function is implemented in
> > the header file of each class. Here's an example for the class
> > NewtonSolver:
> >
> >   /// Default parameter values
> >   static NewParameters default_parameters()
> >   {
> >     NewParameters p("newton_solver");
> >
> >     p.add("maximum_iterations",    50);
> >     p.add("relative_tolerance",    1e-9);
> >     p.add("absolute_tolerance",    1e-10);
> >     p.add("convergence_criterion", "residual");
> >     p.add("method",                "full");
> >     p.add("report",                true);
> >
> >     return p;
> >   }
> >
> > The parameter values must be explicitly set in the constructor by a
> > call to the function default_parameters(). This function is static
> > which means it cannot be placed in the base class Variable and then
> > inherited.
> >
> > 3. Nested parameter sets are handled explicitly from the parent to the
> > child. This means that the parent must both add the parameters of the
> > child (which makes it possible to set those parameters for the parent
> > without an error message about an illegal parameter name) and also
> > propagate those values to the child when appropriate. Here's an
> > example for the class VariationalProblem:
> >
> >   /// Default parameter values
> >   static NewParameters default_parameters()
> >   {
> >     NewParameters p("variational_problem");
> >
> >     p.add("linear_solver", "direct");
> >     p.add("symmetric", false);
> >
> >     p.add(NewtonSolver::default_parameters());
> >     p.add(LUSolver::default_parameters());
> >     p.add(KrylovSolver::default_parameters());
> >
> >     return p;
> >   }
> >
> >   LUSolver solver;
> >   solver.parameters.update(parameters["lu_solver"]);
> 
> I think we should add new parameter set by reference and not by value. Then we 
> should be able to populate the childs default parameters with the parameters 
> of the parents. Something like this:
> 
>   p.add(NewtonSolver::parameters);
>   p.add(LUSolver::parameters);
>   p.add(KrylovSolver::parameters); 
> 
> (Is this the correct syntax?)
> 
> The add by reference also makes it possible for a user to collect all 
> parameters used in an application into a single parameter set. This set can 
> then be used to update all parameters in the application.

I began doing this, but I got into difficulties. Consider the
following example. A user writes:

 VariationalProblem problem(a, L, bc);
 problem.parameters["newton_solver"]("relative_tolerance") = 1e-16;

For this to work the nested parameter set for the Newton solver must e
created already in the constructor of VariationalProblem. But at this
time, the NewtonSolver has not been created. It gets created later
when the user calls solve().

I didn't see an easy way around this.

-- 
Anders



> Johan
> 
> > 4. So in summary, there are more things to think about with the new
> > parameter system:
> >
> >   a. Inherit from Variable (or just declare the parameters variable)
> >   b. Implement default_parameters()
> >   c. Assign parameters = default_parameters()
> >   d. Add parameters for "childs"
> >   e. Propagate parameter values to "childs"
> >
> > It might be possible simplify this. Let's think about it.
> >
> > 5. The old global prefixes "Krylov", "ODE" have been removed.
> >
> > 6. It remains to move the few remaining global parameters to a common
> > global parameter set.
> 
>

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