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++.
