On Thursday 07 May 2009 18:54:04 Anders Logg wrote:
I've added some of the requested features to the parameter system,
some pushed and some sitting here in a local repository. But the
current design makes it a pain to add new features. A single change
will make it necessary to add a function in at least 5 different
classes.
So I'm thinking of reimplementing and simplifying the parameter
system. I think I know how to make it simpler.
But before I do that, does anyone have opinions on the
design/implementation? Is there any third-party library that we
could/should use (maybe something in boost)?
It would be nice to have something that easely could be transferable to
Python.
Having a base class let say Parameterized and then let all inherit this to be
able to define parameters will not work well for the shared_ptr interface we
have. We have problems with the Variable class, which does not work for the
derived shared_ptr classes e.g. Function. I would rather have classes that
have a parameter rather than beeing.
Also by defining a parameter(list/dict) class which can be accessed as a dict
let us make the transition to python smoother.
ParameterDict p = solver.default_params();
p["abs_tol"] = 1e-9;
By defining some templated check classes we could controll the assignment. In
the Solver:
...
ParameterDict& default_params(){
if (!_par)
{
_par = new ParameterDict();
_par->add_param("abs_tol",new RangeCheck<double>(1e-15,0,1));
vector<string> * allowed_prec = new Vector<string>();
allowed_prec->push_back("ilu");
allowed_prec->push_back("amg");
allowed_prec->push_back("jacobi");
_par->add_param("prec",new OptionCheck<string>("ilu"),allowed_prec));
_par->add_param("nonsense","jada"); // No checks
}
}
Well, I admit that the above code is not beautiful, and others can probably
make it cleaner and spot errors. The point is that RangeCheck and OptionCheck
can be derived from a ParCheck class that overloads the operator=(). This
will just call a private set function which is defined in the derived
classes, and which do the check.
The to and from file can be implemented in the ParameterDict body. The checks
do not have to be written or read, as a ParameterDict can only read in
allready predefined parameters, and the check will be done when the file is
read.
The option parser ability can also be implemented in ParameterDict using boost
or other libraries, based on the registered parameters.
I have implemented something like this in Python, and the above is a try to
scetch something similare in c++.
