On Tuesday 01 December 2009 11:21:00 Garth N. Wells wrote: > Johan Hake wrote: > > On Tuesday 01 December 2009 11:06:43 you wrote: > >> Anders Logg wrote: > >>> On Tue, Dec 01, 2009 at 09:59:18AM -0800, Johan Hake wrote: > >>>> On Tuesday 01 December 2009 00:45:50 Anders Logg wrote: > >>>>> Would it help to add a new class on the C++ side that is used only > >>>>> for passing array data back and forth between C++ and Python? We have > >>>>> had this before (SimpleArray) and it would be fairly easy to extend > >>>>> the C++ with extra functions in the interface that use SimpleArray > >>>>> instead of std::vector. > >>>>> > >>>>> Then perhaps we can have one single typemap that hits SimpleArray > >>>>> everywhere and converts it to a NumPy array. > >>>> > >>>> Yes, something in that direction is what I had in mind. In addition we > >>>> could also add a foo.array() function to get a NumPy view from this > >>>> class. This would be nice when we do not want to have all the > >>>> communication through typemaps, but actually using the SimpleArray in > >>>> Python as return argument from some function that wants to resize the > >>>> array. > >>>> > >>>> We would also need some stuff to handle memory management. > >>>> > >>>> I see two fundamental ways such a class could be used: > >>>> 1) A replacement for the previous use of double/uint/int*, now > >>>> std::vector 2) A replacement for communication using std::vector where > >>>> resize flexibility is needed. > >>>> > >>>> I think 1, speaks for it self. 2 is where we need to resize any passed > >>>> vector. This goes for GenericMatrix.getrow, foo.intersection, > >>>> GenericFunction.comput_vertex_values. > >>>> > >>>>> And the work would be to add the extra stuff on the C++ side. The > >>>>> advantage would be less complex wrapper code and that Garth and I > >>>>> are capable of handling the complexities on the C++ side. > >>>> > >>>> Yes this must be a goal. I agree that the present SWIG situation has > >>>> grown out of hands. > >>>> > >>>>> But what I don't understand is why it would be easier to write a > >>>>> typemap for SimpleArray than for std::vector. Both of them use > >>>>> contiguous memory. > >>>> > >>>> Yes, but in std::vector it is now way, I suppose, to prevent a vector > >>>> to delete its data when it goes out of scope. This is necessary in a > >>>> typical in typemap. > >>> > >>> ok, let's create a very flexible array class that is targeted at > >>> simple communication between C++ and Python/NumPy. We had a class > >>> before named SimpleArray. We might call it NumPyArray or PythonArray. > >> > >> Can we just call it Array? It will be visible in the C++ interface (e.g. > >> in eval) so it would be good to have a nice name. > > > > Agree. > > > >>> I have created a blueprint: > >>> > >>> https://blueprints.launchpad.net/dolfin/+spec/array-typemaps > >> > >> I'll add something. I was thinking already about this. With a smart > >> pointer to the underlying data we should be to devise an elegant memory > >> model and be able to tell an Array object when it does and doesn't own > >> the data upon construction, and be able to change during execution. > > > > Sounds fancy. > > > >>> We can fill out the details together. > >>> > >>>> I will fix the interface of getrow this evening. I was about to do it > >>>> yesterday, but instead I got grumpy :) But a good night sleep makes > >>>> wonders! > >>> > >>> Good! :-) > >>> > >>> Will you make a fast/temporary fix so that we can get ready for a > >>> release of 0.9.5 and then we can move the PythonArray implementation > >>> to a future release? > >> > >> The fast fix would be revert back to the > >> > >> eval(double*, std::vector<double>&) > >> > >> interface. No point wasting time on typemaps for std::vector if we're > >> not going to use them. > > > > Fell free to make this change, I have a fool proof plan for the other > > temporary fix though. No new typemaps, just reusing old ones. > > OK, we need to make a decision. > > Option 1: Revert changes to eval. > > Option 2: Get SWIG working with the eval(std::vector<double>&, const > std::vector<double>&) interface. > > What's it going to be? I'm inclined to Option 1 since it requires no > work and it's been well tested.
Isn't the amount of files that are touched with option 1 much larger (all cpp/demos)? But if you do the changes feel free. I can take a look at it this evening if there's something left to do. The new expression.py should at least still be working I think, only compile_expressions.py needs an update. Johan > Garth > > > Johan > > > >> Garth > >> > >>> -- > >>> Anders > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
