> 2008/4/15, Dag Lindbo <[EMAIL PROTECTED]>: >> Thanks Martin! It is much clearer now. My main concern here is as a >> "user", >> since a release is forthcoming. I only wish to clarify things here for >> the >> benefit of (myself and) other users. Comments below. >> >> Martin Sandve Alnæs wrote: >> >> > 2008/4/15, Dag Lindbo <[EMAIL PROTECTED]>: >> > >> > > Hello! >> > > >> > > A lot has happened on the Vector/Function/<backend>Vector interface >> the >> > > last weeks. For clarity, I would like to have a little "summing up" >> > > thread. That is, I think it would be beneficial to explicitly show >> how >> > > the new interface is intended to be used. Sounds good? Here are >> some >> > > situations, to which I propose solutions. Please correct if these >> are >> > > not in line with the intended interface, or if there are better >> ones. >> > > >> > > How to: >> > > *) Get reference to Vector from a (discrete) Function u >> > > Vector& v = dynamic_cast<Vector&>(u.vector()); >> > > >> > >> > Why would you want that? >> > All dolfin library code will now use GenericVector references. >> > This way it will also work with f.ex. uBlasVector objects directly. >> > >> >> I understand that Generic* is used for all internal DOLFIN code. >> >> It is still not clear how "application code", i.e. an actual solver for >> a >> user, is supposed to do this. Is GenericVector from now on part of the >> public interface of DOLFIN? (sorry if I'm repeating this question) > > > Actually, I think you've pointed out a user interface problem here. > We can in general go from Vector to backend-type, but not the other way > around. > > You _can_ do this: > Vector& v = dynamic_cast<Vector&>(u.vector()); > _if_ your code has been using Vector consistently. > It will throw a std::bad_cast exception otherwise. > > But that will limit that part of your code to built-in dolfin backends, > which > is one of the things we're trying to avoid by using GenericVector& > everywhere. > > On the other hand, if you use > GenericVector& v = u.vector(); > this does, as you say, make GenericVector enter user code alongside > Vector, > which was something Anders didn't want to begin with (if I remember > correctly?). > > From Python, this is not an issue.
In C++ user code, I guess that you can use your own typedef for the Generic* /Johan > -- > Martin > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
